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 A241689 #11 Mar 28 2025 13:29:23
%S A241689 0,0,0,0,0,0,0,0,0,0,0,4,22,68,156,320,584,1008,1622,2520,3734,5428,
%T A241689 7612,10488,14126,18744,24390,31436,39914,50212,62390,76932,93918,
%U A241689 113960,137058,163896,194632,229988,270018,315712,367106,425220,490164,563080,644096
%N A241689 Number of Sidon subsets of {1,...,n} of size 5.
%C A241689 A Sidon set is a set of natural numbers A={a_1,a_2,...}, finite or infinite, such that all pairwise sums a_i+a_j (i <= j) are different.
%e A241689 a(12)=4 since the only subsets of {1,...,12} satisfying the required conditions are {1,2,5,10,12}, {1,3,8,9,12}, {1,3,8,11,12}, and {1,4,5,10,12}.
%t A241689 SidonQ[l__] := If[Length[Join[Plus @@@ Subsets[l, {2}], 2 l]] == Length[Union[Join[Plus @@@ Subsets[l, {2}], 2 l]]], True, False]
%t A241689 Table[Length@Select[Subsets[Range[n], {5}], SidonQ[#] &], {n, 1, 30}]
%Y A241689 Column k=5 of A381476.
%Y A241689 Cf. A054578.
%K A241689 nonn
%O A241689 1,12
%A A241689 _Carl Najafi_, Apr 27 2014