cp's OEIS Frontend

A173757 Numbers k such that exactly one of k^2 + k + 1 and k^2 + k + 11 is prime.

%I A173757 #12 Sep 08 2022 08:45:50
%S A173757 0,4,7,9,13,14,16,18,21,23,24,25,27,28,29,30,33,34,39,45,47,50,51,52,
%T A173757 54,56,57,58,59,60,61,66,67,68,69,71,73,77,81,83,84,85,89,90,93,94,96,
%U A173757 99,100,103,105,106,108,110,111,113,114,117,119,122,123,124,125,127,130
%N A173757 Numbers k such that exactly one of k^2 + k + 1 and k^2 + k + 11 is prime.
%C A173757 Numbers k such that either k^2+k+1 or k^2+k+11 is prime, but not both. - _R. J. Mathar_, Mar 01 2010
%e A173757 0 is in the sequence because 0^2+0+1 = 1 is nonprime and 0^2+0+11 = 11 is prime; 1 is not in the sequence because 1^2+1+1 = 3 is prime and 1^2+1+11 = 13 is also prime, 10 is not in the sequence because 10^2+10+1 = 111 is nonprime and 10^2+10+11 = 121 is also nonprime; 14 is in the sequence because 14^2+14+1 = 211 is prime and 14^2+14+11 = 221 is nonprime.
%o A173757 (Magma) [ n: n in [0..130] | IsPrime(k+1) ne IsPrime(k+11) where k is n^2+n ]; // _Klaus Brockhaus_, Feb 26 2010
%Y A173757 Cf. A048058.
%K A173757 nonn
%O A173757 1,2
%A A173757 _Juri-Stepan Gerasimov_, Feb 23 2010
%E A173757 Edited and extended by _Klaus Brockhaus_, Feb 26 2010
%E A173757 More terms from _R. J. Mathar_, Mar 01 2010