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A093067
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Expansion of (eta(q)eta(q^5)/(eta(q^3)eta(q^15)))^2 in powers of q.
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0
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1, -2, -1, 4, -3, -2, 11, -6, -11, 20, -15, -16, 43, -24, -32, 76, -48, -58, 144, -84, -97, 238, -144, -172, 398, -234, -279, 636, -372, -428, 1012, -582, -678, 1564, -906, -1028, 2389, -1362, -1576, 3560, -2046, -2320, 5290, -2988, -3407, 7700, -4371, -4928
(list; graph; refs; listen; history; internal format)
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OFFSET
| -1,2
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COMMENTS
| Euler transform of period 15 sequence [ -2,-2,0,-2,-4,0,-2,-2,0,-4,-2,0,-2,-2,0,...].
G.f. A(x)=y satisfies 0=f(A(x),A(x^2)) where f(u,v)=u^3+v^3-4uv(u+v)-u^2v^2-9uv.
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PROG
| (PARI) a(n)=local(X); if(n<-1, 0, n++; X=x+x*O(x^n); polcoeff((eta(X)*eta(X^5)/eta(X^3)/eta(X^15))^2, n))
(PARI) a(n)=local(A, u, v); if(n<-1, 0, A=1/x; for(k=0, n, u=A+x*O(x^k); v=subst(u, x, x^2); A+=x^k*polcoeff(u^3+v^3-4*u*v*(u+v)-u^2*v^2-9*u*v, k-5)/2); polcoeff(A, n))
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CROSSREFS
| Apart from constant term, same as A058509.
Sequence in context: A140169 A124731 A143122 * A098122 A159931 A159755
Adjacent sequences: A093064 A093065 A093066 * A093068 A093069 A093070
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KEYWORD
| sign
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AUTHOR
| Michael Somos, Mar 17 2004
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