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A131126 Expansion of (eta(q^4)^5/( eta(q)^2* eta(q^2)* eta(q^8)^2) )^2 in powers of q. +0
3
1, 4, 16, 48, 128, 312, 704, 1504, 3072, 6036, 11488, 21264, 38400, 67864, 117632, 200352, 335872, 554952, 904784, 1457136, 2320128, 3655296, 5702208, 8813472, 13504512, 20523996, 30952544, 46340832, 68901888, 101777112, 149403264 (list; graph; listen)
OFFSET

0,2

FORMULA

Expansion of (phi(q^2) / phi(-q))^2 in powers of q where phi() is a Ramanujan theta function.

Expansion of ((phi(q) / phi(-q))^2 + 1) / 2 in powers of q where phi() is a Ramanujan theta function.

Euler transform of period 8 sequence [ 4, 6, 4, -4, 4, 6, 4, 0, ...].

EXAMPLE

1 + 4*q + 16*q^2 + 48*q^3 + 128*q^4 + 312*q^5 + 704*q^6 + 1504*q^7 + ...

PROGRAM

(PARI) {a(n) = local(A); if( n<0, 0, A = x * O(x^n); polcoeff( (eta(x + A)^2 * eta(x^2 + A) * eta(x^8 + A)^2 / eta(x^4 + A)^5)^-2, n))}

CROSSREFS

4 * A107035(n) = a(n) unless n=0. A014969(n) = 2 * a(n) unless n=0.

Sequence in context: A006009 A100625 A071009 this_sequence A159964 A058922 A034918

Adjacent sequences: A131123 A131124 A131125 this_sequence A131127 A131128 A131129

KEYWORD

nonn

AUTHOR

Michael Somos, Jun 15 2007

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Last modified November 27 14:50 EST 2009. Contains 167570 sequences.


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