A370795 Centered square numbers which are products of four distinct primes (or tetraprimes).

99905, 107185, 242905, 350285, 363805, 372385, 433381, 569245, 590785, 630565, 692665, 752765, 907205, 942565, 1026745, 1076045, 1090765, 1105585, 1227745, 1275205, 1333345, 1467185, 1526005, 1647113, 1661665, 1761565, 1810705, 1911013, 2026085, 2317705, 2395861, 2470865

Offset: 1

Author

Massimo Kofler, Mar 02 2024

Keywords

• nonn

Comments

All terms are odd.

Examples

			99905 = 5 * 13 * 29 * 53 = (2 * 223 * 224) + 1.
107185 = 5 * 13 * 17 * 97 = (2 * 231 * 232) + 1.
242905 = 5 * 13 * 37 * 101 = (2 * 348 * 349) + 1
		

Crossrefs

Intersection of A046386 and A001844.

Programs

Mathematica

Select[Table[2*n*(n + 1) + 1, {n, 0, 1200}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} &] (* Amiram Eldar, Mar 02 2024 *)

Formula

a(n) == 1 (mod 4).