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Search: id:A107597
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| 1, 1, 2, 4, 8, 17, 38, 87, 205, 493, 1203, 2969, 7389, 18504, 46561, 117596, 297883, 756388, 1924484, 4904830, 12519121, 31995286, 81864992, 209681349, 537562018, 1379332297, 3542013533, 9102191107, 23406301490, 60226845008, 155059899921
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Limit a(n+1)/a(n) = (sqrt(5)+3)/2.
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FORMULA
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a(n) = (A051286(n) + A000045(n+1))/2, where A000045(n+1) = Fibonacci(n+1) and A051286(n) = Whitney number of level n.
G.f.: (1/(1-x-x^2) +1/sqrt((1+x+x^2)* (1-3*x+x^2)))/2. - Michael Somos Jul 27 2007
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PROGRAM
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(PARI) a(n)=(sum(k=0, n, binomial(n-k, k)^2)+fibonacci(n+1))/2
(PARI) {a(n)= if(n<0, 0, polcoeff( (1/(1-x-x^2) +1/sqrt((1+x+x^2)* (1-3*x+x^2)+ x*O(x^n)))/2, n))} /* Michael Somos Jul 27 2007 */
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CROSSREFS
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Cf. A107105, A051286, A000045.
Sequence in context: A006196 A089796 A112482 this_sequence A082499 A100131 A119685
Adjacent sequences: A107594 A107595 A107596 this_sequence A107598 A107599 A107600
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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), May 22 2005
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