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Search: id:A128231
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| A128231 |
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Expansion of exp(x)/(1 - x^3/3!), where a(n) = 1 + C(n,3)*a(n-3). |
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3
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| 1, 1, 1, 2, 5, 11, 41, 176, 617, 3445, 21121, 101806, 757901, 6040607, 37057385, 344844956, 3382739921, 25199021801, 281393484097, 3277874983450, 28726884853141, 374253333849011, 5047927474513001, 50875313074912712
(list; graph; listen)
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OFFSET
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0,4
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EXAMPLE
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E.g.f.: exp(x)/(1 - x^3/3!) = 1 + x + 1*x^2/2! + 2*x^3/3! + 5*x^4/4! + 11*x^5/5! + 41*x^6/6! +... + a(n)*x^n/n! +...
where a(n) = 1 + n*(n-1)*(n-2)*a(n-3)/3!.
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MAPLE
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restart: G(x):=2*exp(-x)/(x^3/3!+1): f[0]:=G(x): for n from 1 to 26 do f[n]:=diff(-f[n-1], x) od: x:=0: seq(f[n]/2, n=0..23); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 03 2009]
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PROGRAM
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(PARI) a(n)=n!*polcoeff(exp(x+x*O(x^n))/(1-x^3/3! +x*O(x^n)), n)
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CROSSREFS
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Cf. A087214, A128230, A128232.
Sequence in context: A106886 A007700 A071313 this_sequence A121981 A088148 A088149
Adjacent sequences: A128228 A128229 A128230 this_sequence A128232 A128233 A128234
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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 20 2007
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