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A121593
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Expansion of (eta(q^7)/eta(q))^4 in powers of q.
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0
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1, 4, 14, 40, 105, 252, 574, 1236, 2564, 5124, 9948, 18788, 34685, 62664, 111132, 193672, 332325, 561996, 937958, 1546132, 2519825, 4062888, 6486008, 10257324, 16079389, 24996636, 38555216, 59025820, 89728900, 135486960, 203274344
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| Euler transform of period 7 sequence [ 4, 4, 4, 4, 4, 4, 0, ...].
G.f.: x*(Product_{k>0} (1-x^(7k))/(1-x^k))^4.
G.f. A(x) satisfies 0=f(A(x), A(x^2)) where f(u, v)= (u+v)*(u-v)^2 -u*v*(1+7*u)*(1+7*v).
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PROG
| (PARI) {a(n)=local(A); if(n<1, 0, n--; A=x*O(x^n); polcoeff( (eta(x^7+A)/eta(x+A))^4, n))}
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CROSSREFS
| Sequence in context: A001938 A066368 A160463 * A160527 A023003 A001872
Adjacent sequences: A121590 A121591 A121592 * A121594 A121595 A121596
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KEYWORD
| nonn
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AUTHOR
| Michael Somos, Aug 09 2006
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