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%I #18 May 19 2021 22:09:27
%S 40,41,44,49,56,65,76,81,82,84,87,89,91,96,102,104,109,117,121,122,
%T 123,126,127,130,136,138,140,143,147,155,159,161,162,163,164,170,172,
%U 173,178,184,185,186,187,190,201,204,205,207,208,209,213,215,216,217,218
%N Numbers k such that k^2 + k + 41 is semiprime.
%C Subsequence of A007634. Numbers in A007634 but not in here are 420, 431, 491, 492, 514, 533, 573, etc. (A097822). - _R. J. Mathar_, Aug 17 2013
%H Shyam Sunder Gupta, <a href="/A228184/b228184.txt">Table of n, a(n) for n = 1..4760</a>
%e a(3) = 44 is in the sequence because 44^2 + 44 + 41 = 43*47 is semiprime.
%t a = {}; Do[
%t If[PrimeOmega[x^2 + x + 41] == 2, AppendTo[a, x]], {x, 1, 500}]; a
%Y Cf. A002837, A001358, A007634.
%K nonn,less
%O 1,1
%A _Shyam Sunder Gupta_, Aug 15 2013
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