A367792 Centered 10-gonal numbers which are products of two primes.
361, 451, 551, 781, 1711, 2101, 2761, 3781, 4061, 4351, 5611, 5951, 7031, 7801, 8201, 8611, 9031, 10351, 10811, 11281, 11761, 12751, 13261, 14311, 15961, 16531, 17111, 17701, 21451, 23461, 26281, 28501, 29261, 30031, 30811, 34861, 35701, 40951, 41861, 42781, 45601, 46561
Offset: 1
Keywords
Examples
A062786(9) = 361 = 5 * 9 * (9-1) + 1 = 19 * 19. A062786(10) = 451 = 5 * 10 * (10-1) + 1 = 11 * 41. A062786(11) = 551 = 5 * 11 * (11-1) + 1 = 19 * 29.
Programs
-
Mathematica
Select[Table[5*n*(n-1) + 1, {n, 1, 100}], PrimeOmega[#] == 2 &] (* Amiram Eldar, Nov 30 2023 *)