A109546 - OEIS

%I #1 Sep 21 2005 03:00:00

%S 5,11,53,203,821,3275,13109,52427,209717,838859,3355445,13421771,

%T 53687093,214748363,858993461,3435973835,13743895349,54975581387,

%U 219902325557,879609302219,3518437208885,14073748835531,56294995342133

%N (4^(n+1)-(-1)^n 9 )/5.

%C a(n)= 2^n th coefficient of - eta(z)^5 eta (3z) eta (6z)^4/ eta(2z)^4.

%F a(0)=-1, a(n)=4*a(n-1)-(-1)^n * 9, n >=1.

%e a(3)=53, since (4^4+9)/5=53

%o (PARI) for (n=1,100,print( (4^(n+1)-(-1)^n *9 )/5));

%K nonn

%O 1,1

%A Kok Seng Chua (chuaks(AT)ihpc.a-star.edu.sg), Aug 30 2005