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 A131927 Series reversion of x * (1 - 9*x) / (1 - x). 2
 0, 1, 8, 136, 2888, 68680, 1749896, 46707976, 1289214152, 36496595656, 1053849164552, 30918300671368, 919029058099784, 27617782977715528, 837674888992142984, 25610757376777402888, 788450850824647610312 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS The Hankel transform of this sequence is 72^C(n+1,2) . LINKS FORMULA a(n) = Sum_{k, 0<=k<=n} A086810(n,k)*8^k . G.f.: (1+x-sqrt(1-34*x+x^2))/18. - Emeric Deutsch, Nov 19 2007 a(n) = - a(n-1) + 9 * Sum_{k=1..n-1} a(k) * a(n-k) if n>1. - Michael Somos, Jul 23 2011 EXAMPLE x + 8*x^2 + 136*x^3 + 2888*x^4 + 68680*x^5 + 1749896*x^6 + 46707976*x^7 + ... MAPLE G:=(1+x-sqrt(1-34*x+x^2))*1/18: Gser:=series(G, x=0, 21): seq(coeff(Gser, x, n), n =0..17); - Emeric Deutsch, Nov 19 2007 PROG (PARI) {a(n) = local(A); if( n<1, 0, A = vector(n); A[1] = 1; for( k=2, n, A[k] = - A[k-1] + 9 * sum( j=1, k-1, A[j] * A[k-j])); A[n])} /* Michael Somos, Jul 23 2011 */ CROSSREFS Sequence in context: A069988 A072072 A195614 * A132869 A036915 A049211 Adjacent sequences:  A131924 A131925 A131926 * A131928 A131929 A131930 KEYWORD nonn AUTHOR Philippe DELEHAM, Oct 29 2007 EXTENSIONS More terms from Emeric Deutsch, Nov 19 2007 STATUS approved

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