A359624 Centered triangular numbers which are products of three distinct primes.

1054, 1786, 2110, 2710, 4294, 5134, 6634, 7885, 8326, 10210, 12835, 13114, 14554, 17014, 22510, 24769, 25546, 26335, 30889, 32635, 36271, 42085, 44635, 45154, 47794, 49414, 52174, 52735, 53866, 56746, 58510, 61510, 63346, 66466, 68374, 71614, 73594, 75601, 76954, 84610, 88210

Offset: 1

Author

Massimo Kofler, Jan 08 2023

Keywords

• nonn

Comments

A squarefree subsequence of centered triangular numbers.

Examples

			1054 = 2 * 17 * 31 = (3 * 27 * (27 - 1) / 2) + 1.
1786 = 2 * 19 * 47 = (3 * 35 * (35 - 1) / 2) + 1.
7885 = 5 * 19 * 83 = (3 * 73 * (73 - 1) / 2) + 1.
		

Crossrefs

Intersection of A005448 and A007304.

Programs

Mathematica

Select[Table[3*n*(n - 1)/2 + 1, {n, 1, 250}], FactorInteger[#][[;; , 2]] == {1, 1, 1} &] (* Amiram Eldar, Jan 08 2023 *)