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Search: id:A127782
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| A127782 |
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G.f. satisfies: A(x) = 1 + x*A(x+x^2). |
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+0
7
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| 1, 1, 1, 2, 4, 11, 33, 114, 438, 1845, 8458, 41823, 221539, 1250269, 7481758, 47278652, 314374316, 2192798077, 16000160519, 121831654450, 965946444587, 7958739329386, 68023023892680, 602115897105136, 5511499584735858
(list; graph; listen)
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OFFSET
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0,4
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COMMENT
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Equals eigensequence of triangle A026729 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Jan 16 2009]
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FORMULA
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a(n) = Sum_{k=0..[n/2]} C(n-k,k)*a(n-k-1) for n>0 with a(0)=1.
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PROGRAM
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(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(i=0, n, A=1+x*subst(A, x, x+x^2)); polcoeff(A, n)} (PARI) a(n)=if(n==0, 1, sum(k=0, n\2, binomial(n-k, k)*a(n-k-1)))
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CROSSREFS
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A026729 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Jan 16 2009]
Sequence in context: A026164 A025191 A035354 this_sequence A002846 A123444 A123473
Adjacent sequences: A127779 A127780 A127781 this_sequence A127783 A127784 A127785
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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), Jan 28 2007
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