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 A120411 #13 Dec 13 2015 23:08:17
%S A120411 1,3,7,15,30,59,114,219,416,783,1461,2722,5048,9341,17243,31674,58037,
%T A120411 105936,192522,348832
%N A120411 If A is a set of integers, the (2-fold) sumset consists of all the numbers which can be written as the sum of two (not necessarily distinct) elements in A. a(n) is the number of subsets of [1,2n] which are sumsets for some set of positive integers.
%C A120411 The relation a(n+1)-a(n) = A190820(n) seems to hold. - _Giovanni Resta_, Jan 15 2013
%e A120411 a(5)=30 because two of the 31 (nonempty) subsets of [1,5], namely {1,2,4,5} and {1,2,3,4,5} have the sumset {2,3,4,5,6,7,8,9,10} and no two other subsets of [1,5] have the same sumset.
%K A120411 nonn,more
%O A120411 1,2
%A A120411 _David S. Newman_, Jul 05 2006
%E A120411 a(14)-a(20) from _Carl Najafi_, Jan 15 2013