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%I #16 Aug 09 2015 01:03:42
%S 1,1,1,1,5,1,1,9,15,5,1,29,3,5,3,15,5,1,17,19,3,11,23,13,19,19,7,9,15,
%T 71,5,19,49,1,11,15,7,1,21,39,5,11,1,19,55,11,71,39,23,29,7,61,49,15,
%U 1,11,17,37,15,31,23,19,3,1,33,21,37,21,17,9,41,43,5,7,25,1,19,37,23,5,27,5,37,31,15,85,67,43,79,77
%N a(n)=least odd number k such that 3*k*2^n-1 is a prime number
%H Pierre CAMI, <a href="/A210651/b210651.txt">Table of n, a(n) for n = 1..7725</a>
%p A210651 := proc(n)
%p for k from 1 by 2 do
%p if isprime(3*k*2^n-1) then
%p return k;
%p end if;
%p end do:
%p end proc: # _R. J. Mathar_, Mar 29 2012
%o PFGW64 and SCRIPTIFY from Primeform group
%o Command: pfgw64 -f in.txt
%o in.txt file :
%o SCRIPT
%o DIM nn,0
%o DIM kk
%o DIMS tt
%o OPENFILEOUT myfile,a(n).txt
%o LABEL loopn
%o SET nn,nn+1
%o IF nn>7725 THEN END
%o SET kk,-1
%o LABEL loopk
%o SET kk,kk+2
%o SETS tt,%d,%d\,;nn;kk
%o PRP 3*kk*2^nn-1,tt
%o IF ISPRP THEN GOTO a
%o IF ISPRIME THEN GOTO a
%o GOTO loopk
%o LABEL a
%o WRITE myfile,tt
%o GOTO loopn
%Y Cf. A126717.
%K nonn
%O 1,5
%A _Pierre CAMI_, Mar 27 2012
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