# Smarandache function

The Smarandache function $S\colon\mathbb{Z}^{+}\to\mathbb{Z}^{+}$ is defined as follows: $S(n)$ is the smallest integer such that $S(n)!$ is divisible by $n$. For example, the number 8 does not divide $1!$, $2!$, $3!$, but does divide $4!$. Therefore $S(8)=4$. Another study of $S(n)$ has been published by http://genealogy.math.ndsu.nodak.edu/html/id.phtml?id=12376Aubrey J. Kempner in 1918, and later the function $S(n)$ has been rediscovered and studied by Florentin Smarandache in 1980. A profound study of this function would contribute to the study of prime numbers  in accordance with the following property: if $p$ is a number greater than $4$, then $p$ is a prime if and only if $S(p)=p$. The values of $S(n)$ for $n=1,2,3,\ldots$ are given by Sloane’s (http://planetmath.org/NeilSloane) OEIS http://www.research.att.com/ njas/sequences/?q=A002034A002034.

A list of sixteen s denoted $s_{1}$ to $s_{16}$ have been defined with the use of the Smarandache function $S(n)$, and they should not be confused with the Smarandache constant, which is the smallest solution to the generalized Andrica conjecture.

The first Smarandache constant (Sloane’s (http://planetmath.org/NeilSloane) OEIS http://www.research.att.com/ njas/sequences/?q=A048799A048799) is defined as $\displaystyle s_{1}=\sum_{n=2}^{\infty}\left(S(n)!\right)^{-1}\approx 1.09317\ldots$

The second Smarandache constant $s_{2}$ (Sloane’s (http://planetmath.org/NeilSloane) OEIS http://www.research.att.com/ njas/sequences/?q=A048834A048834) is defined as $\displaystyle s_{2}=\sum_{n=2}^{\infty}\frac{S(n)}{n!}\approx 1.71400629359162\ldots$ and it is an irrational number.

The third Smarandache constant $s_{3}$ (Sloane’s (http://planetmath.org/NeilSloane) OEIS http://www.research.att.com/ njas/sequences/?q=A048835A048835) is defined as $\displaystyle s_{3}=\sum_{n=2}^{\infty}\left(\prod_{i=2}^{n}S(i)\right)^{-1}% \approx 0.719960700043\ldots$.

The series $\displaystyle s_{4}(\alpha)=\sum_{n=2}^{\infty}n^{\alpha}\left(\prod_{i=2}^{n}% S(i)\right)^{-1}$ converges  for a fixed real number $\alpha\geq 1$. Since $s_{4}$ is a function of $\alpha$ it is not a single constant, but an infinite list of them. The values for small $\alpha$ have been computed:

$s_{4}(1)\approx 1.72875760530223\ldots$ (Sloane’s (http://planetmath.org/NeilSloane) OEIS http://www.research.att.com/ njas/sequences/?q=A048836A048836).

$s_{4}(2)\approx 4.50251200619296\ldots$ (Sloane’s (http://planetmath.org/NeilSloane) OEIS http://www.research.att.com/ njas/sequences/?q=A048837A048837).

$s_{4}(3)\approx 13.0111441949445\ldots$ (Sloane’s (http://planetmath.org/NeilSloane) OEIS http://www.research.att.com/ njas/sequences/?q=A048838A048838).

The fifth Smarandache constant $\displaystyle s_{5}=\sum_{n=1}^{\infty}\frac{(-1)^{n-1}S(n)}{n!}$ converges to an irrational number.

Dumitrescu and Seleacu in 1996 showed that the series $\displaystyle s_{7}(r)=\sum_{n=r}^{\infty}\frac{S(n)}{(n+r)!}$ and $\displaystyle s_{8}(r)=\sum_{n=r}^{\infty}\frac{S(n)}{(n-r)!}$ converge for $r\in\mathbb{Z}^{+}$.

The same authors show that the series $\displaystyle s_{9}=\sum_{n=2}^{\infty}\left(\sum_{i=2}^{n}\frac{S(i)}{i!}% \right)^{-1}$ is convergent  .

The series $\displaystyle s_{10}(\alpha)=\sum_{n=2}^{\infty}\left(S(n)\right)^{-\alpha}% \left(S(n)!\right)^{-\frac{1}{2}}$ and $\displaystyle s_{11}(\alpha)=\sum_{n=2}^{\infty}\left(S(n)\right)^{-\alpha}% \left[\left(S(n)-1\right)!\right]^{-\frac{1}{2}}$ converge for $\alpha>1$. These two series also define an infinite list of constants.

If $f:\mathbb{N}\rightarrow\mathbb{R}$ is a function satisfying the condition $\displaystyle f(t)\leq\frac{c}{t^{\alpha}d\left(t!\right)-d\left((t-1)!\right)}$, where $t$ is a positive integer, $d$ denotes the divisor function  , and the given constants $\alpha>1$, $c>1$, then the series $\displaystyle s_{12}(f)=\sum_{n=1}^{\infty}f\left(S(n)\right)$ is convergent.

The series $\displaystyle s_{13}=\sum_{n=1}^{\infty}\left(\prod_{k=1}^{n}S(k)!\right)^{-% \frac{1}{n}}$ is convergent.

The series $\displaystyle s_{14}(\alpha)=\sum_{n=1}^{\infty}\left(S(n)!\right)^{-\frac{3}{% 2}}\left(\log{S(n)}\right)^{-\alpha}$ is convergent for $\alpha>1$.

The series $\displaystyle s_{15}=\sum_{n=1}^{\infty}\frac{2^{n}}{S(2^{n})!}$ is convergent.

The series $\displaystyle s_{16}(\alpha)=\sum_{n=1}^{\infty}\frac{S(n)}{n^{1+\alpha}}$ is convergent for $\alpha>1$.

2. Ashbacher C, Popescu M (1995). An Introduction to the Smarandache Function. Erhus University Press. ISBN 1879585499.

3. Tabirca S, Tabirca T, Reynolds K, Yang LT (2004). http://dx.doi.org/10.1109/ISPDC.2004.15”Calculating Smarandache function in parallel”. Parallel and Distributed Computing, 2004. Third International Symposium on Algorithms  , Models and Tools for Parallel Computing on Heterogeneous Networks,: pp.79-82.

4. Kempner AJ (1918). ”Miscellanea”. http://www.jstor.org/view/00029890/di991004/99p1446d/0 The American Mathematical Monthly 25: 201-210.

6. Smarandache F (1980). ”A Function in Number Theory”. Analele Univ. Timisoara, Ser. St. Math. 43: 79-88.

7. Smarandache F. http://www.gallup.unm.edu/ smarandache/CONSTANT.TXTConstants Involving the Smarandache Function.

8. Muller R (1990). ”Editorial”. http://www.gallup.unm.edu/ smarandache/SFJ1.pdfSmarandache Function Journal 1: 1.

9. Cojocaru I, Cojocaru S (1996). ”The First Constant of Smarandache”. http://www.gallup.unm.edu/ smarandache/SNJ7.pdfSmarandache Notions Journal 7: 116-118.

10. Cojocaru I, Cojocaru S (1996). ”The Second Constant of Smarandache”. http://www.gallup.unm.edu/ smarandache/SNJ7.pdfSmarandache Notions Journal 7: 119-120.

11. Cojocaru I, Cojocaru S (1996). ”The Third and Fourth Constants of Smarandache”. http://www.gallup.unm.edu/ smarandache/SNJ7.pdfSmarandache Notions Journal 7: 121-126.

12. Sandor J (1997). ”On The Irrationality Of Certain Alternative Smarandache Series”. http://www.gallup.unm.edu/ smarandache/SNJ8.pdfSmarandache Notions Journal 8: 143-144.

13. Burton E (1995). ”On Some Series Involving the Smarandache Function”. http://www.gallup.unm.edu/ smarandache/SFJ6.pdfSmarandache Function Journal 6: 13-15.

14. Burton E (1996). ”On Some Convergent Series”. http://www.gallup.unm.edu/ smarandache/SNJ7.pdfSmarandache Notions Journal 7 (1-3): 7-9.

Title Smarandache function SmarandacheFunction 2013-03-22 17:04:15 2013-03-22 17:04:15 dankomed (17058) dankomed (17058) 47 dankomed (17058) Definition msc 11A41 GeneralizedAndricaConjecture