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Search: id:A091188
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| A091188 |
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G.f. A(x) satisfies both A(-x)*A(x) = A(x^2) and xA(x)^2 = B(xA(x^2)) where B(x) = x*(1+x)/(1-x). |
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+0
4
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| 1, 1, 1, 2, 2, 4, 5, 10, 12, 23, 31, 58, 79, 145, 207, 374, 540, 964, 1427, 2522, 3775, 6626, 10050, 17532, 26811, 46561, 71795, 124188, 192661, 332228, 518303, 891340, 1396902, 2396912, 3771822, 6459202, 10199912, 17437727, 27622807, 47152952
(list; graph; listen)
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OFFSET
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0,4
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COMMENT
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This is a special case of sequences with g.f.s that satisfy the more general functional equation xA(x)^m = B(xA(x^m)) originated by Michael Somos; some other examples are A085748, A091190 and A091200.
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PROGRAM
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(PARI) {a(n)=local(A, m); if(n<0, 0, m=1; A=1+O(x); while(m<=n, m*=2; A=x*subst(A, x, x^2); A=(A*(1+A)/(1-A)/x)^(1/2)); polcoeff(A, n))}
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CROSSREFS
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Cf. A085748, A091190, A091200.
Sequence in context: A116651 A135586 A116646 this_sequence A147678 A127712 A032090
Adjacent sequences: A091185 A091186 A091187 this_sequence A091189 A091190 A091191
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Feb 22 2004
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