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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. 2
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.)