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 A016164 Expansion of 1/((1-5x)(1-10x)). 7
 1, 15, 175, 1875, 19375, 196875, 1984375, 19921875, 199609375, 1998046875, 19990234375, 199951171875, 1999755859375, 19998779296875, 199993896484375, 1999969482421875, 19999847412109375, 199999237060546875 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n)= (5^n)*stirling2(n+2, 2), n>=0, with stirling2(n, m)=A008277(n, m). a(n)= -5^n+2*10^n. G.f.: 1/((1-5*x)*(1-10*x)). E.g.f.: diff((((exp(5*x)-1)/5)^2)/2!, x\$2) = -exp(5*x)+2*exp(10*x). Sum(5^(k-1)*5^(n-k)*binomial(n, k),k=1..n). - Zerinvary Lajos, Sep 24 2006 a(0)=1, a(n)=10*a(n-1)+5^n. [From Vincenzo Librandi, Feb 09 2011] MATHEMATICA Join[{a=1, b=15}, Table[c=15*b-50*a; a=b; b=c, {n, 60}]] (* Vladimir Joseph Stephan Orlovsky, Feb 01 2011*) PROG (PARI) Vec(1/((1-5*x)(1-10*x))+O(x^99)) \\ Charles R Greathouse IV, Sep 25 2012 CROSSREFS Second column of triangle A075500. Cf. A075911. Sequence in context: A107395 A036083 A051588 * A000482 A145147 A069379 Adjacent sequences:  A016161 A016162 A016163 * A016165 A016166 A016167 KEYWORD nonn,easy AUTHOR STATUS approved

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