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 A099899 #8 Jul 11 2015 01:05:02
%S A099899 1,5,21,69,277,1349,5141,16453,65813,329029,1381397,4538437,18088213,
%T A099899 88081733,335549461,1073758277,4295033109,21475165509,90195694613,
%U A099899 296357281861,1189724029205,5793998964037,22080762418197,70666170679365
%N A099899 Multiplies by 4 and shifts right under the XOR BINOMIAL transform (A099898).
%C A099899 Equals the XOR BINOMIAL transform of A099898. Also, equals the main diagonal of the XOR difference triangle A099897, in which the central terms of the rows form the powers of 4. See A099884 for the definitions of XOR difference triangle and the XOR BINOMIAL transform.
%F A099899 a(n) = SumXOR_{k=0..n} (C(n-k+[k/2], [k/2])mod 2)*2^k for n>=0. a(n) = SumXOR_{i=0..n} (C(n, i)mod 2)*A099898(n-i), where SumXOR is the analog of summation under the binary XOR operation and C(i, j)mod 2 = A047999(i, j).
%o A099899 (PARI) {a(n)=local(B);B=0;for(k=0,n,B=bitxor(B,binomial(n-k+k\2,k\2)%2*4^k));B}
%Y A099899 Cf. A099884, A099897, A099898.
%K A099899 nonn
%O A099899 0,2
%A A099899 _Paul D. Hanna_, Oct 30 2004