OFFSET
1,1
COMMENTS
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<i | &+[d[2]: d in Factorization(i)] eq 2>; [s: x in [2..200] | IsSemiprime(s) where s is x^2+x+41]; // Bruno Berselli, Aug 15 2013
CROSSREFS
KEYWORD
nonn,less
AUTHOR
Shyam Sunder Gupta, Aug 15 2013
STATUS
approved