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 A099898 #9 May 11 2014 22:43:56
%S A099898 1,4,20,84,276,1108,5396,20564,65812,263252,1316116,5525588,18153748,
%T A099898 72352852,352326932,1342197844,4295033108,17180132436,85900662036,
%U A099898 360782778452,1185429127444,4758896116820,23175995856148,88323049672788
%N A099898 Shifts left and divides by 4 under the XOR BINOMIAL transform (A099899).
%C A099898 Equals the XOR BINOMIAL transform of A099899. Also, equals the leftmost column of the XOR difference triangle A099897, in which the central terms of the rows forms the powers of 4. See A099884 for the definitions of XOR difference triangle and the XOR BINOMIAL transform.
%F A099898 a(0)=1; a(n) = SumXOR_{k=0..n-1} (C(n-1-k+[k/2], [k/2])mod 2)*4^(k+1) for n>0. a(n) = SumXOR_{i=0..n} (C(n, i)mod 2)*A099899(n-i), where SumXOR is the analog of summation under the binary XOR operation and C(k, i)mod 2 = A047999(k, i).
%o A099898 (PARI) {a(n)=local(B);B=0;if(n==0,B=1, for(k=0,n-1, B=bitxor(B,binomial(n-1-k+k\2,k\2)%2*4^(k+1))));B}
%Y A099898 Cf. A099884, A099897, A099899.
%K A099898 nonn
%O A099898 0,2
%A A099898 _Paul D. Hanna_, Oct 30 2004