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

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 A360637

Adjacent sequences: A027666 A027667 A027668 * A027670 A027671 A027672

Keyword

nonn

Author

Masanobu Kaneko (mkaneko(AT)math.kyushu-u.ac.jp)

Status

approved