This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A379859 #13 Jan 05 2025 09:58:57 %S A379859 1,1,9,110,2121,53834,1720105,66197578,2984752113,154358553986, %T A379859 9009411908001,585917934419498,42018536835853369,3294423846094650658, %U A379859 280362373171289449209,25739124908062020925034,2535728977438902352557921,266836955238122741966767874,29872121613650590137264191665 %N A379859 Expansion of e.g.f. (1/x) * Series_Reversion( x * exp(x) * (1 - x*exp(x))^2 ). %H A379859 <a href="/index/Res#revert">Index entries for reversions of series</a> %F A379859 E.g.f. A(x) satisfies A(x) = exp(-x*A(x))/(1 - x * A(x) * exp(x*A(x)))^2. %F A379859 a(n) = (n!/(n+1)) * Sum_{k=0..n} (-n+k-1)^(n-k) * binomial(2*n+k+1,k)/(n-k)!. %o A379859 (PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(serreverse(x*exp(x)*(1-x*exp(x))^2)/x)) %o A379859 (PARI) a(n) = n!*sum(k=0, n, (-n+k-1)^(n-k)*binomial(2*n+k+1, k)/(n-k)!)/(n+1); %Y A379859 Cf. A377546, A379860. %Y A379859 Cf. A379684. %K A379859 nonn %O A379859 0,3 %A A379859 _Seiichi Manyama_, Jan 04 2025