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 A174055 #12 Mar 03 2016 02:24:21
%S A174055 9,13,17,21,37,41,45,65,69,93,133,137,141,161,165,189,257,261,285,381,
%T A174055 8197,8201,8205,8225,8229,8253,8321,8325,8349,8445,16385,16389,16413,
%U A174055 16509,24573,131077,131081,131085,131105,131109,131133,131201,131205,131229,131325,139265,139269,139293,139389,147453,262145,262149
%N A174055 Sums of three Mersenne primes.
%H A174055 Robert Israel, <a href="/A174055/b174055.txt">Table of n, a(n) for n = 1..969</a>
%F A174055 A000668(i) + A000668(j) + A000668(k), with integers i,j,k not necessarily distinct. The subsequence of prime sums of three Mersenne primes is A174056.
%e A174055 a(1) = 3 + 3 + 3 = 9. a(2) = 3 + 3 + 7 = 13. a(3) = 3 + 7 + 7 = 17. a(4) = 7 + 7 + 7 = 21. a(5) = 3 + 3 + 31 = 37. a(6) = 3 + 7 + 31 = 41.
%p A174055 N:= 10^6: # to get all terms <= N
%p A174055 for n from 1 while numtheory:-mersenne([n]) < N do od:
%p A174055 S:= {seq(numtheory:-mersenne([i]),i=1..n-1)}:
%p A174055 sort(convert(select(`<=`,{seq(seq(seq(s+t+u,s=S),t=S),u=S)},N),list)); # _Robert Israel_, Mar 02 2016
%Y A174055 Cf. A000668, A155877, A166484, A171251, A171252, A171253, A171254, A171255, A174056, A174057.
%K A174055 nonn
%O A174055 1,1
%A A174055 _Jonathan Vos Post_, Mar 06 2010
%E A174055 More terms from _Max Alekseyev_, Oct 15 2012
%E A174055 Edited by _Robert Israel_, Mar 02 2016