A279831 Numbers that are centered k-gonal numbers for two or more values of k.

1, 7, 13, 16, 19, 22, 25, 31, 37, 43, 46, 49, 55, 61, 64, 67, 73, 76, 79, 85, 91, 97, 103, 106, 109, 111, 115, 121, 127, 133, 136, 139, 141, 145, 148, 151, 154, 157, 163, 166, 169, 172, 175, 181, 187, 190, 191, 193, 196, 199, 205, 211, 217, 221, 223, 226, 229, 232, 235, 241, 247, 253, 256

Offset

1,2

Comments

Numbers satisfying 1 + n*m*(m+1)/2 for two or more values of (n,m), where n>=0 m>1.

Numbers in this sequence appear in A101321 at least three times (because the second column contains every positive integer).

Links

Daniel Sterman, Table of n, a(n) for a(n)<1000

Example

19 is in the sequence because 19 is both a centered triangular number and a centered hexagonal number.

Crossrefs

Cf. A090428 (rough equivalent for polygonal numbers).

Cf. A101321 (table of all centered polygonal numbers).

Cf. A275340 (list of nontrivial centered polygonal numbers).

Sequence in context: A233301 A274255 A233747 * A102797 A233062 A381116

Adjacent sequences: A279828 A279829 A279830 * A279832 A279833 A279834

Keyword

nonn

Author

Daniel Sterman, Dec 20 2016

Status

approved