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 A222054 O.g.f.: Sum_{n>=0} (n^4*x)^n/(1-n^4*x)^n * exp(-n^4*x/(1-n^4*x)) / n!. 2
 1, 1, 128, 90621, 193322261, 933620289929, 8632521193856886, 136885314823146617517, 3443427946573913689696192, 129667338445150206244162849650, 6988095504452769015520539806767120, 520011535068804196524689647521015780176 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS FORMULA a(n) = Sum_{k=1..n} C(n-1,k-1) * S2(4*n,k) for n>0 with a(0)=1. EXAMPLE O.g.f.: A(x) = 1 + x + 128*x^2 + 90621*x^3 + 193322261*x^4 +... where A(x) = 1 + x/(1-x)*exp(-x/(1-x)) + 2^8*x^2/(1-2^4*x)^2*exp(-2^4*x/(1-2^4*x))/2! + 3^12*x^3/(1-3^4*x)^3*exp(-3^4*x/(1-3^4*x))/3! + 4^16*x^4/(1-4^4*x)^4*exp(-4^4*x/(1-4^4*x))/4! +... simplifies to a power series in x with integer coefficients. PROG (PARI) {a(n)=polcoeff(sum(k=0, n+1, (k^4*x)^k/(1-k^4*x)^k*exp(-k^4*x/(1-k^4*x+x*O(x^n)))/k!), n)} for(n=0, 20, print1(a(n), ", ")) (PARI) {Stirling2(n, k)=n!*polcoeff(((exp(x+x*O(x^n))-1)^k)/k!, n)} {a(n)=if(n==0, 1, sum(k=1, n, binomial(n-1, k-1) * Stirling2(4*n, k)))} for(n=0, 20, print1(a(n), ", ")) CROSSREFS Cf. A134055, A174845, A222053, A217913, A008277. Sequence in context: A220301 A323541 A016795 * A283926 A016831 A103348 Adjacent sequences:  A222051 A222052 A222053 * A222055 A222056 A222057 KEYWORD nonn AUTHOR Paul D. Hanna, Mar 08 2013 STATUS approved

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Last modified April 21 06:42 EDT 2019. Contains 322310 sequences. (Running on oeis4.)