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 A090957 #28 Sep 08 2022 08:45:12
%S A090957 1,30,495,7280,101745,1381380,18407025,242082720,3153092085,
%T A090957 40763504210,523886186670,6700599687600,85360889543475,
%U A090957 1083790852008480,13721016740550360,173280964190422080,2183615911571190525
%N A090957 a(n) = 1/(Integral_{x=0..1} (x^4 - x^5)^n dx).
%H A090957 G. C. Greubel, <a href="/A090957/b090957.txt">Table of n, a(n) for n = 0..915</a>
%F A090957 a(n) = 1/B(4*n+1,n+1) = (5*n+1)!/(n! * (4*n)!), where B(p,q) is Euler's beta function. - _Emeric Deutsch_, Jul 03 2009
%F A090957 a(n) ~ sqrt(n)*5^(5*n+3/2) / (sqrt(Pi)*2^(8*n+3/2)). - _Vaclav Kotesovec_, Aug 15 2017
%p A090957 seq(factorial(5*n+1)/(factorial(n)*factorial(4*n)), n = 0 .. 16); # _Emeric Deutsch_, Jul 03 2009
%t A090957 Table[1/Integrate[(x^4-x^5)^n,{x,0,1}],{n,0,20}] (* _Harvey P. Dale_, Jan 02 2013 *)
%t A090957 Table[1/Beta[4*n+1,n+1], {n,0,20}] (* _G. C. Greubel_, Feb 03 2019 *)
%o A090957 (PARI) for (n = 0, 20, pol = (x^4 - x^5)^n; s = 0; for (i = 4*n, 5*n, s += polcoeff(pol, i)/(i + 1)); print(1/s)); \\ _David Wasserman_, Feb 22 2006
%o A090957 (PARI) vector(20, n, n--; (5*n+1)!/(n!*(4*n)!)) \\ _G. C. Greubel_, Feb 03 2019
%o A090957 (Magma) [Factorial(5*n+1)/(Factorial(n)*Factorial(4*n)): n in [0..20]]; // _G. C. Greubel_, Feb 03 2019
%o A090957 (Sage) [1/beta(4*n+1,n+1) for n in range(20)] # _G. C. Greubel_, Feb 03 2019
%Y A090957 Cf. A002457, A090816, A090969.
%K A090957 nonn
%O A090957 0,2
%A A090957 Al Hakanson (hawkuu(AT)excite.com), Feb 27 2004
%E A090957 More terms from _David Wasserman_, Feb 22 2006