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A224856 Numbers n such that 90*n + 29 and 90*n + 31 are twin primes.

%I A224856 #21 Jul 23 2013 20:51:41
%S A224856 0,6,7,11,14,28,30,33,37,39,47,53,61,65,74,75,76,77,84,88,91,110,128,
%T A224856 139,152,158,170,179,180,194,195,201,215,216,228,229,251,271,282,305,
%U A224856 308,312,334,336,345,362,366,368,370,373,383,384,410,411,413,427,450
%N A224856 Numbers n such that 90*n + 29 and 90*n + 31 are twin primes.
%F A224856 A201739 INTERSECT A201819.
%p A224856 a:= proc(n) option remember; local k; for k from 1+
%p A224856        `if`(n=1, -1, a(n-1)) while not (isprime(29+(90*k))
%p A224856         and isprime(31+(90*k))) do od; k
%p A224856     end:
%p A224856 seq(a(n), n=1..100);  # _Alois P. Heinz_, Jul 23 2013
%t A224856 Select[Range[0, 499], PrimeQ[90# + 29] && PrimeQ[90# + 31] &] (* copied from: _Alonso del Arte_, Jul 22 2013 *)
%Y A224856 Cf. A201739, A201819.
%K A224856 nonn,easy
%O A224856 1,2
%A A224856 _J. W. Helkenberg_, Jul 22 2013