|
%I #4 Dec 05 2013 19:56:45
%S 2,5,31,311,3733,59729,1194581,57339889,1605516893,22477236503,
%T 1933042339259,143045133105167,2574812395893007,87543621460362239,
%U 700348971682897913,58829313621363424693,1411903526912722192633
%N a(1) = 2, a(n) is the least prime of the form 2k*a(n-1)+1 where 2k is the least even number not used earlier.
%e a(2) = 5 = 2*2+1, But a(3) = 31 though 11= 5*2 +1 is also prime.
%o Contribution from _Rick L. Shepherd_, Sep 08 2009: (Start)
%o (PARI) {a=[2]; terms=1; used=Set();
%o while(terms<30, k2=0; until(isprime(k2*a[terms]+1),
%o until(setsearch(used,k2)==0, k2=k2+2));
%o a=concat(a,k2*a[terms]+1); terms++; used=setunion(used,Set([k2]))); a} (End)
%K nonn
%O 1,1
%A _Amarnath Murthy_, Mar 13 2004
%E a(6) onwards by _Rick L. Shepherd_, Sep 08 2009
| 