A382451 Centered pentagonal numbers which are the products of four distinct primes.

5406, 12426, 20026, 23766, 40641, 55131, 83266, 115026, 118266, 136306, 142206, 145806, 176226, 184281, 205206, 209526, 245706, 279726, 284766, 315951, 326706, 371526, 387106, 407031, 413106, 419226, 425391, 498406, 505126, 553426, 623751, 638826, 672106, 685131

Offset: 1

Author

Massimo Kofler, Mar 26 2025

Keywords

• nonn

Examples

			A005891(46) = 5406 = (5*46^2 + 5*46 + 2)/2 = 2*3*17*53.
A005891(70) = 12426 = (5*70^2 + 5*70 + 2)/2 = 2*3*19*109.
A005891(127) = 40641 = (5*127^2 + 5*127 + 2)/2 = 3*19*23*31.
		

Crossrefs

Intersection of A005891 and A046386.

Cf. A364610.

Programs

Mathematica

Select[Table[5*n*(n+1)/2+1, {n, 0, 600}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} &] (* Amiram Eldar, Mar 26 2025 *)