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 A331520 #4 Jan 19 2020 09:20:09
%S A331520 1,1,1,2,2,5,3,9,7,24,8,33,17,77,27,134,66,351,67,419,135,908,204,
%T A331520 1469,479,3643,553,4572,1182,10227,1889,17125,4641,43640,4642,48283,
%U A331520 9285,101211,13929,158786,32504,384441,37153,465259,78957,1020640,125414,1675453
%N A331520 a(0) = a(1) = 1; a(n+2) = Sum_{k=0..n} (binomial(n,k) mod 2) * a(k).
%C A331520 Shifts 2 places left under the modulo 2 binomial transform.
%F A331520 a(n) = Sum_{k=0..n} (-1)^A010060(n-k) * (binomial(n, k) mod 2) * a(k+2).
%t A331520 a[0] = a[1] = 1; a[n_] := a[n] = Sum[Mod[Binomial[n - 2, k], 2] a[k], {k, 0, n - 2}]; Table[a[n], {n, 0, 47}]
%Y A331520 Cf. A007476, A010060, A047999, A166966.
%K A331520 nonn
%O A331520 0,4
%A A331520 _Ilya Gutkovskiy_, Jan 19 2020