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

1,1

Links

Table of n, a(n) for n=1..42.

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

Adjacent sequences: A367789 A367790 A367791 * A367793 A367794 A367795

Keyword

nonn

Author

Massimo Kofler, Nov 30 2023

Status

approved