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# oblong number

An integer of the form $n\cdot(n+1)$ or $n^{2}+n$. The partial sum

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

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

Synonym:

heteromecic number, pronic number

Type of Math Object:

Definition

Major Section:

Reference

## Mathematics Subject Classification

11D85*no label found*

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## Versions

(v4) by CompositeFan 2013-03-22