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 A088812 #16 Feb 16 2025 08:32:51
%S A088812 0,0,0,1,2,6,21,49,119,266,626,1315,2859,5878,12798,26038,54485,
%T A088812 109976,230159,462634,945846,1897597,3893242,7798862,15834340,
%U A088812 31695551,64315161,128693477,259241944,518614045,1046344906,2092965726,4206946359,8414499960
%N A088812 Number of subsets of {1, ..., n} that are neither double-free nor sum-free.
%H A088812 Fausto A. C. Cariboni, <a href="/A088812/b088812.txt">Table of n, a(n) for n = 0..75</a>
%H A088812 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Double-FreeSet.html">Double-Free Set</a>
%H A088812 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Sum-FreeSet.html">Sum-Free Set</a>
%H A088812 Reinhard Zumkeller, <a href="/A088808/a088808.txt">Illustration of initial terms</a>
%F A088812 a(n) = 2^n - A088813(n) = A088808(n)-A088811(n) = A088809(n)-A088810(n).
%K A088812 nonn
%O A088812 0,5
%A A088812 _Reinhard Zumkeller_, Oct 19 2003
%E A088812 Terms a(28) and beyond from _Fausto A. C. Cariboni_, Sep 29 2020