Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #6 Nov 21 2013 12:48:36
%S 1,1,2,1,3,1,2,2,5,1,2,2,4,2,4,4,9,1,2,2,4,2,4,4,8,2,4,4,8,4,8,8,17,1,
%T 2,2,4,2,4,4,8,2,4,4,8,4,8,8,16,2,4,4,8,4,8,8,16,4,8,8,16,8,16,16,33,
%U 1,2,2,4,2,4,4,8,2,4,4,8,4,8,8,16,2,4,4,8,4,8,8,16,4,8,8
%N A modular binomial sum sequence.
%C a(2^n)=A094373(n). a(2^n-1)=1,1,1,2,4,8,16,...
%H Harvey P. Dale, <a href="/A101691/b101691.txt">Table of n, a(n) for n = 0..1000</a>
%F a(n)=sum{k=0..n, mod(binomial(2n-2, k), 2)}
%t Table[Sum[Mod[Binomial[2n-2,k],2],{k,0,n}],{n,0,100}] (* _Harvey P. Dale_, Oct 20 2011 *)
%Y Cf. A048896.
%K easy,nonn
%O 0,3
%A _Paul Barry_, Dec 11 2004