A364610 Centered pentagonal numbers which are products of three distinct primes.

1266, 1626, 2806, 3706, 4731, 6126, 7426, 7701, 9766, 10726, 13506, 15801, 18706, 19581, 25251, 26266, 26781, 31641, 35106, 36906, 40006, 50766, 52926, 56626, 57381, 62806, 69306, 71826, 74391, 76126, 85101, 90726, 93606, 95551, 96531, 99501, 106606, 108681, 109726, 117181, 121551, 123766

Offset: 1

Author

Massimo Kofler, Sep 07 2023

Keywords

• nonn

Examples

			A005891(22) = 1266 = (5*22^2 + 5*22 + 2)/2 = 2 * 3 * 211.
A005891(25) = 1626 = (5*25^2 + 5*25 + 2)/2 = 2 * 3 * 271.
A005891(33) = 2806 = (5*33^2 + 5*33 + 2)/2 = 2 * 23 * 61.
		

Crossrefs

Intersection of A005891 and A007304.

Programs

Mathematica

Select[Table[5*n*(n + 1)/2 + 1, {n, 0, 225}], FactorInteger[#][[;; , 2]] == {1, 1, 1} &] (* Amiram Eldar, Sep 07 2023 *)