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Search: id:A093073
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| A093073 |
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Expansion of eta(q)*eta(q^2)/(eta(q^9)eta(q^18)) in powers of q. |
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| 1, -1, -2, 1, 0, 2, 1, 0, 0, -1, 0, -4, -1, 0, 4, 0, 0, 2, 1, 0, -8, 2, 0, 8, 0, 0, 2, -2, 0, -16, -3, 0, 16, -1, 0, 4, 4, 0, -28, 4, 0, 28, 1, 0, 8, -4, 0, -48, -6, 0, 46, -1, 0, 12, 5, 0, -80, 8, 0, 76, 1, 0, 20, -8, 0, -126, -10, 0, 120, -2, 0, 32, 11, 0, -196, 14, 0, 184, 4, 0, 48
(list; graph; listen)
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OFFSET
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-1,3
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COMMENT
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Euler transform of period 18 sequence [ -1,-2,-1,-2,-1,-2,-1,-2,0,-2,-1,-2,-1,-2,-1,-2,-1,...].
G.f. A(x)=y satisfies 0=f(A(x),A(x^2)) where f(u,v)=u^4+v^4 -uv((u+v)^2+9(u+v)+uv(u+v+4)).
a(3n-1)=A062242(n), a(3n+1)=-2*A092848(n). a(3n)=0, if n>0.
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PROGRAM
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(PARI) a(n)=if(n<-1, 0, n++; X=x+x*O(x^n); polcoeff(eta(X)*eta(X^2)/eta(X^9)/eta(X^18), n))
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CROSSREFS
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Essentially same as A058531.
Sequence in context: A093201 A067613 A058531 this_sequence A156319 A083650 A030204
Adjacent sequences: A093070 A093071 A093072 this_sequence A093074 A093075 A093076
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KEYWORD
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sign
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AUTHOR
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Michael Somos, Mar 17 2004
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