This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A171251 #21 Jun 02 2025 02:13:23
%S A171251 6,10,14,34,38,62,130,134,158,254,8194,8198,8222,8318,16382,131074,
%T A171251 131078,131102,131198,139262,262142,524290,524294,524318,524414,
%U A171251 532478,655358,1048574,2147483650,2147483654,2147483678,2147483774,2147491838
%N A171251 Sums of two (not necessarily distinct) Mersenne primes (A000668).
%C A171251 All terms are even, since all terms of A000668 are odd. This motivates to introduce A171252 = (1/2) * A171251, see there for further information.
%H A171251 Jonathan Vos Post, <a href="https://web.archive.org/web/*/http://list.seqfan.eu/oldermail/seqfan/2010-March/003808.html">Sums of three Mersenne primes, and prime sums of three Mersenne primes</a>, SeqFan list, Mar 5, 2010.
%F A171251 A171251(n) = 2*A171252(n) = A000668(i) + A000668(j) where n = i*(i-1)/2+j.
%t A171251 With[{mps=Select[2^Range[50]-1,PrimeQ]},Union[Total/@Tuples[mps,2]]] (* _Harvey P. Dale_, Aug 11 2012 *)
%t A171251 With[{mps=2^MersennePrimeExponent[Range[10]]-1},Union[Total/@Tuples[mps,2]]] (* _Harvey P. Dale_, Mar 20 2025 *)
%o A171251 (PARI) concat(vector(#A000668,i,vector(i,j,A000668[i]+A000668[j]))) /* having defined A000668 as vector with initial terms of A000668 */
%Y A171251 Cf. A000668, A171252.
%K A171251 nonn
%O A171251 1,1
%A A171251 _M. F. Hasler_, Mar 06 2010