A027669 - OEIS

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A027669

Numbers n such that for some m, the sum of the first m n-gonal numbers is again an n-gonal number.

3, 4, 6, 8, 10, 11, 14, 17, 20, 23, 26, 29, 30, 32, 35, 38, 41, 43, 44, 47, 50, 53, 56, 59, 60, 62, 65, 68, 71, 74, 77, 80, 83, 86, 88, 89, 92, 95, 98 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,1`
	LINKS	`Table of n, a(n) for n=1..39.`
	FORMULA	`k-th n-gonal number is k+(n-2)*(k^2-k)/2).`
	CROSSREFS	`Cf. A027696.` `Sequence in context: A091555 A184398 A024665 * A027696 A027440 A169866` `Adjacent sequences: A027666 A027667 A027668 * A027670 A027671 A027672`
	KEYWORD	`nonn`
	AUTHOR	`Masanobu Kaneko (mkaneko(AT)math.kyushu-u.ac.jp)`
	STATUS	`approved`

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Last modified May 28 18:24 EDT 2022. Contains 354122 sequences. (Running on oeis4.)