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A107882 Column 1 of triangle A107880. 4
1, 2, 5, 19, 104, 766, 7197, 82910, 1136923, 18141867, 330940109, 6803936050, 155839142185, 3938383850350, 108934529005948, 3275059508166297, 106388204134734785, 3714826559490125850, 138796913898027894261 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

FORMULA

G.f.: 1 = Sum_{k>=0} a(k)*x^k*(1-x)^(2 + k*(k+1)/2).

EXAMPLE

1 = 1*(1-x)^2 + 2*x*(1-x)^3 + 5*x^2*(1-x)^5 +

19*x^3*(1-x)^8 + 104*x^4*(1-x)^12 + 766*x^5*(1-x)^17 +...

PROG

(PARI) {a(n)=polcoeff(1-sum(k=0, n-1, a(k)*x^k*(1-x+x*O(x^n))^(2+k*(k+1)/2)), n)}

CROSSREFS

Cf. A107880, A107881, A107883.

Sequence in context: A076669 A093502 A009311 * A192445 A089126 A113346

Adjacent sequences:  A107879 A107880 A107881 * A107883 A107884 A107885

KEYWORD

nonn

AUTHOR

Paul D. Hanna (pauldhanna(AT)juno.com), Jun 04 2005

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Last modified February 14 23:16 EST 2012. Contains 205687 sequences.