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 A202474 Coefficients of y^(n-1) in Product_{k=1..n} (1 + k*y + y^2) for n >= 1. 3
 1, 3, 14, 80, 539, 4179, 36630, 358056, 3860922, 45519870, 582466235, 8038684290, 119018991779, 1881685721265, 31638175704546, 563703015007056, 10609073237333432, 210305960538762456, 4379808881917047898, 95604092878386437940, 2182706554812339958778 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Table of n, a(n) for n=1..21. FORMULA E.g.f.: 1/(1-x) * Sum_{n>=0} log(1 - x)^(2*n+1) / (n!*(n+1)!). EXAMPLE E.g.f.: A(x) = x + 3*x^2/2! + 14*x^3/3! + 80*x^4/4! + 539*x^5/5! + 4179*x^6/6! + 36630*x^7/7! + 358056*x^8/8! + 3860922*x^9/9! + 45519870*x^10/10! + ... The coefficients in Product_{k=1..n} (1+k*x+x^2), n>=0, form the triangle: [1]; [(1), 1, 1]; [1,(3), 4, 3, 1]; [1, 6, (14), 18, 14, 6, 1]; [1, 10, 39, (80), 100, 80, 39, 10, 1]; [1, 15, 90, 285, (539), 660, 539, 285, 90, 15, 1]; [1, 21, 181, 840, 2339, (4179), 5038, 4179, 2339, 840, 181, 21, 1]; [1, 28, 329, 2128, 8400, 21392, (36630), 43624, 36630, 21392, 8400, 2128, 329, 28, 1]; ... the coefficients in parenthesis form the initial terms of this sequence. MATHEMATICA Flatten[{1, Table[Coefficient[Expand[Product[1 + k*x + x^2, {k, 1, n+1}]], x^n], {n, 1, 20}]}] (* Vaclav Kotesovec, Feb 10 2015 *) PROG (PARI) {a(n) = polcoeff(prod(k=1, n, 1 + k*x + x^2 +x*O(x^n)), n-1)} for(n=1, 30, print1(a(n), ", ")) CROSSREFS Cf. A201826, A201950, A202476. Sequence in context: A212391 A000264 A009053 * A347001 A354325 A346966 Adjacent sequences: A202471 A202472 A202473 * A202475 A202476 A202477 KEYWORD nonn AUTHOR Paul D. Hanna, Dec 19 2011 EXTENSIONS Changed offset to 1 to agree with e.g.f. - Paul D. Hanna, Mar 02 2019 STATUS approved

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Last modified June 9 23:28 EDT 2023. Contains 363183 sequences. (Running on oeis4.)