A361696 Semiprimes of the form k^2 + 5.
6, 9, 14, 21, 69, 86, 201, 329, 446, 489, 581, 681, 734, 789, 905, 1094, 1769, 1941, 2606, 2921, 3254, 3369, 3849, 3974, 4101, 4629, 4766, 6729, 7061, 7401, 8105, 8654, 9609, 9806, 10409, 10821, 11669, 12326, 13929, 17429, 17961, 19049, 20741, 23109, 23721, 24341, 27561, 30281, 31334, 32405
Offset: 1
Examples
69 is a term because 8^2 + 5 = 69 = 3*23.
Links
- Paolo Xausa, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Select[Range[200]^2 + 5, PrimeOmega[#] == 2 &] (* Paolo Xausa, Aug 21 2025 *)
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PARI
isok(k) = issquare(k-5) && (bigomega(k)==2); \\ Michel Marcus, Mar 27 2023
Formula
a(n) = A242333(n)^2 + 5.