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 A278179 a(n) is the denominator of intersection number , n>=2. 2
 240, 144, 48, 8, 96, 1, 32, 1, 32, 1, 8, 1, 16, 1, 64, 1, 32, 1, 32, 1, 64, 1, 16, 1, 16, 1, 8, 1, 16, 1, 128, 1, 32, 1, 32, 1, 64, 1, 64, 1, 64, 1, 4, 1, 8, 1, 32, 1, 16, 1, 16, 1, 32, 1, 16, 1, 16, 1, 8, 1, 16, 1, 256, 1, 32, 1, 32, 1, 64, 1, 64, 1, 64, 1, 16, 1, 32, 1, 128, 1, 64, 1, 64, 1, 128 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS For 'intersection numbers' see Section 1 in Itzykson and Zuber paper. LINKS Gheorghe Coserea, Table of n, a(n) for n = 2..1025 Stavros Garoufalidis, Marcos Marino, Universality and asymptotics of graph counting problems in nonorientable surfaces, arXiv:0812.1195 [math.CO], 2008. C. Itzykson, J.-B. Zuber, Combinatorics of the Modular Group II: the Kontsevich integrals, arXiv:hep-th/9201001, 1991. FORMULA a(n) = denominator((3*n-3)!*4^n/((5*n-5)*(5*n-3)) * A269418(n)/A269419(n)) for n >= 2. EXAMPLE 7/240, 1225/144, 1816871/48, 7723802625/8, 8591613499103635/96, ... PROG (PARI) A269418_seq(N) = { my(y = vector(N)); y[1] = 1/48; for (n = 2, N, y[n] = (25*(n-1)^2-1)/48 * y[n-1] + 1/2*sum(k = 1, n-1, y[k]*y[n-k])); concat(-1, y); }; seq(N) = { my(y = A269418_seq(N+2)); vector(N, g, (3*g)! * 4^(g+1) / ((5*g)*(5*g+2)) * y[g+2]); }; apply(denominator, seq(85)) CROSSREFS Cf. A269418, A269419, A278178 (numerator). Sequence in context: A298621 A299587 A078151 * A100748 A072235 A298453 Adjacent sequences: A278176 A278177 A278178 * A278180 A278181 A278182 KEYWORD nonn,frac AUTHOR Gheorghe Coserea, Nov 13 2016 STATUS approved

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Last modified November 28 02:38 EST 2022. Contains 358406 sequences. (Running on oeis4.)