A219957 - 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