A027669 Numbers k such that for some m, the sum of the first m k-gonal numbers is again a k-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, 101, 104, 107, 110, 113, 116, 119, 122, 125, 128, 131, 134, 137, 140, 143, 145, 146, 149, 152, 155, 158, 161, 164, 167, 170, 173, 176, 179, 182, 185, 188, 191, 194, 197, 200, 203, 206, 209, 212, 215, 218, 221, 224, 227, 230, 233, 236, 239, 242, 245, 248, 251, 254, 257, 260, 263, 266, 269, 272, 275, 276

Offset: 1

Author

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

Keywords

• nonn

Comments

The m-th k-gonal number is m+(k-2)*(m^2-m)/2.

3*j+2 = A016789(j) is a term for j >= 2.

Crossrefs

Cf. A016789, A027696, A344410.

Formula

Set union of A027696 and A016789, excluding elements 2 and 5. - Max Alekseyev, Feb 27 2025

Extensions

More terms from Max Alekseyev, Feb 27 2025