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 A383450 #7 May 04 2025 08:02:15 %S A383450 2,21,180,1430,10920,81396,596904,4326300,31081050,221760825, %T A383450 1573537680,11114897976,78215948720,548652722520,3838040704080, %U A383450 26784871943928,186537501038070,1296717366119175,8999440181955300,62366467037593950,431633967218324640,2983755440056831440,20603495011611002400,142131208489591604400 %N A383450 2nd diagonal (from right) in A104978. %H A383450 N. J. Wildberger and Dean Rubine, <a href="https://doi.org/10.1080/00029890.2025.2460966">A Hyper-Catalan Series Solution to Polynomial Equations, and the Geode</a>, Amer. Math. Monthly (2025). See table on page 12. %F A383450 From _Peter Luschny_, May 04 2025: (Start) %F A383450 a(n) = (3*n + 4)! / (2*n!*(3 + 2*n)!). %F A383450 a(n) = [x^n] 2*hypergeom([5/3, 7/3], [5/2], (27*x)/4). (End) %p A383450 From _Peter Luschny_, May 04 2025: (Start) %p A383450 a := n -> (3*n + 4)!/(n!*2*(2 + 2*n + 1)!): seq(a(n), n = 0..23); %p A383450 gf := 2*hypergeom([5/3, 7/3], [5/2], (27*x)/4): %p A383450 ser := series(gf, x, 25): seq(coeff(ser, x, k), k = 0..23); (End) %Y A383450 Cf. A104987. %K A383450 nonn %O A383450 0,1 %A A383450 _N. J. A. Sloane_, May 02 2025