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 A228183 Semiprimes generated by the Euler polynomial x^2 + x + 41. 8
 1681, 1763, 2021, 2491, 3233, 4331, 5893, 6683, 6847, 7181, 7697, 8051, 8413, 9353, 10547, 10961, 12031, 13847, 14803, 15047, 15293, 16043, 16297, 17071, 18673, 19223, 19781, 20633, 21797, 24221, 25481, 26123, 26447, 26773, 27101, 29111, 29797, 30143 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This is a subsequence of A145292. The first numbers in A145292 but not in here are 176861, 186233, 241613, 242597, ... LINKS Shyam Sunder Gupta and K. D. Bajpai, Table of n, a(n) for n = 1..10000 (first 4760 terms from Shyam Sunder Gupta) EXAMPLE The semiprime 1763 = 41^2 + 41 + 41 = 41*43 is in the sequence. MATHEMATICA a = {}; Do[If[PrimeOmega[x^2 + x + 41] == 2, AppendTo[a, x^2 + x + 41]], {x, 1, 200}]; a (* For the b-file: *) n = 0; Do[t = k^2 + k + 41; If[PrimeOmega[t] == 2, n++; Print[n, " ", t]], {k, 30000}] (* K. D. Bajpai, Apr 22 2014 *) PROG (MAGMA) IsSemiprime:=func; [s: x in [2..200] | IsSemiprime(s) where s is x^2+x+41]; // Bruno Berselli, Aug 15 2013 CROSSREFS Cf. A001358, A145292. Sequence in context: A172667 A221204 A145292 * A175897 A322745 A189654 Adjacent sequences:  A228180 A228181 A228182 * A228184 A228185 A228186 KEYWORD nonn,less AUTHOR Shyam Sunder Gupta, Aug 15 2013 STATUS approved

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Last modified July 24 15:05 EDT 2021. Contains 346273 sequences. (Running on oeis4.)