oblong number

An integer of the form n(n+1) or n2+n. The partial sum


works, too. From this it follows that one can also multiply the nth triangular numberMathworldPlanetmath. Plenty of other relations to various polygonal numbersMathworldPlanetmath 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.

Title oblong number
Canonical name OblongNumber
Date of creation 2013-03-22 15:50:19
Last modified on 2013-03-22 15:50:19
Owner CompositeFan (12809)
Last modified by CompositeFan (12809)
Numerical id 4
Author CompositeFan (12809)
Entry type Definition
Classification msc 11D85
Synonym heteromecic number
Synonym pronic number