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A367792
Centered 10-gonal numbers which are products of two primes.
0
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
1,1
EXAMPLE
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.
MATHEMATICA
Select[Table[5*n*(n-1) + 1, {n, 1, 100}], PrimeOmega[#] == 2 &] (* Amiram Eldar, Nov 30 2023 *)
CROSSREFS
Intersection of A062786 and A001358.
Sequence in context: A003799 A003930 A137607 * A325882 A255787 A219340
KEYWORD
nonn
AUTHOR
Massimo Kofler, Nov 30 2023
STATUS
approved