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 A134173 #18 Feb 10 2024 04:40:37 %S A134173 1,3,8,68,2106,223776,80532200,98945392200,421225839051260, %T A134173 6310402120912239968,337401124757628967733136, %U A134173 65171905481441631827737564000,45944096973025484590366745753166436 %N A134173 a(n) = Sum_{k=0..n} binomial(n,k)*binomial(2^k,n). %H A134173 G. C. Greubel, <a href="/A134173/b134173.txt">Table of n, a(n) for n = 0..59</a> %F A134173 G.f.: Sum_{n>=0} log(1+(2^n+1)*x)^n/n!. %F A134173 From _Vaclav Kotesovec_, Jul 02 2016: (Start) %F A134173 a(n) ~ binomial(2^n,n). %F A134173 a(n) ~ 2^(n^2) / n!. %F A134173 a(n) ~ 2^(n^2 - 1/2) * exp(n) / (sqrt(Pi) * n^(n+1/2)). %F A134173 (End) %p A134173 a:=proc(n) options operator, arrow: sum(binomial(n,k)*binomial(2^k,n),k=0..n) end proc: seq(a(n),n=0..13); # _Emeric Deutsch_, Jan 27 2008 %t A134173 Table[Sum[Binomial[n,k]*Binomial[2^k,n],{k,0,n}],{n,0,15}] (* _Vaclav Kotesovec_, Jul 02 2016 *) %o A134173 (PARI) for(n=0,25, print1(sum(k=0,n, binomial(n,k)*binomial(2^k,n)), ", ")) \\ _G. C. Greubel_, Mar 21 2017 %K A134173 easy,nonn %O A134173 0,2 %A A134173 _Paul D. Hanna_ and _Vladeta Jovovic_, Jan 13 2008 %E A134173 More terms from _Emeric Deutsch_, Jan 27 2008