0,3

Row sums of Riordan array (1/(1+x+x^2),x/(1+x)^2), A122917.

a(n)=4*sqrt(3)*cos(2*pi*n/3+pi/6)/9+2(n+1)sin(2*pi*n/3+pi/6)/3; a(n)=sum{k=0..n, A057078(k)A057078(n-k)};

Sequence in context: A146478 A098804 A113072 this_sequence A129903 A023616 A099491

Adjacent sequences: A122915 A122916 A122917 this_sequence A122919 A122920 A122921

easy,sign

Paul Barry (pbarry(AT)wit.ie), Sep 19 2006