Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #9 Dec 06 2012 14:27:27
%S 19,25,31,35,37,49,53,59,65,85,89
%N Numbers expressible as 2*p + 3*q exactly in two ways, where p and q are primes (not necessarily distinct).
%e 89 = 2*37 + 3*5 = 2*19 + 3*17.
%t mx = 1000; s = Table[0, {mx}]; Do[a = 2 Prime[i] + 3 Prime[k]; s[[a]]++, {k, PrimePi[(mx - 4)/3]}, {i, PrimePi[(mx - 3 Prime[k])/2]}]; Flatten@Position[s, 2]
%Y Cf. A079026, A219955, A219956.
%K nonn,fini,full
%O 1,1
%A _Zak Seidov_, Dec 02 2012