PlanetMath: oblong number

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oblong number

(Definition)

An integer of the form $n \cdot (n + 1)$ or . The partial sum

$\displaystyle \sum_{i = 0}^n 2i$

works, too. From this it follows that one can also multiply the th triangular number. Plenty of other relations to various polygonal numbers can be obtained.

The first few terms are 0, 2, 6, 12, 20, 30, 42, 56, 72, 90, 110, and are listed in A002378 of Sloane's OEIS.

"oblong number" is owned by CompositeFan. [ owner history (1) ]

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Other names:

heteromecic number, pronic number

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Cross-references: OEIS, terms, polygonal numbers, relations, triangular number, partial sum, integer
There are 5 references to this entry.

This is version 1 of oblong number, born on 2006-04-08.
Object id is 7814, canonical name is OblongNumber.
Accessed 2159 times total.

Classification:

11D85 (Number theory :: Diophantine equations :: Representation problems)

Pending Errata and Addenda

None.

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