A356095 Tetrahedral numbers which are products of three distinct primes.

165, 286, 455, 969, 1771, 4495, 9139, 12341, 32509, 176851, 437989, 657359, 939929, 3737581, 9290431, 21084251, 26536591, 39338069, 44101441, 61690919, 92568571, 112805879, 289442201, 381588019, 439918931, 495593039, 711215371, 815946449, 1008077071, 1103914379

Offset: 1

Author

Massimo Kofler, Jul 26 2022

Keywords

• nonn

Comments

A squarefree subsequence of tetrahedral numbers T(n) = C(n+2,3) = n*(n+1)*(n+2)/6.

Examples

			165 = 9*10*11/6 = 3*5*11
286 = 11*12*13/6 = 2*11*13
455 = 13*14*15/6 = 5*7*13
9139 = 37*38*39/6 = 13*19*37
		

Crossrefs

Intersection of A000292 and A007304.

Subsequence of A070755.

Programs

Mathematica

Select[Table[n*(n + 1)*(n + 2)/6, {n, 1, 2000}], FactorInteger[#][[;; , 2]] == {1, 1, 1} &] (* Amiram Eldar, Jul 26 2022 *)