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 A071416 #20 Feb 16 2025 08:32:46
%S A071416 1,2,1,2,1,6,1,2,1,2,1,4,1,2,15,2,1,6,1,20,3,2,1,12,1,2,1,28,1,2,1,2,
%T A071416 3,2,7,4,1,2,1,20,1,42,1,4,45,2,1,12,1,2,3,4,1,6,1,8,3,2,1,12,1,2,3,2,
%U A071416 5,66,1,4,3,10,1,36,1,2,15,4,77,6,1,20,1,2,1,28,5,2,3,88,1,10,91,4,1,2,5
%N A071416 a(n) = gcd(n, binomial(2*n, n)).
%C A071416 a(n) = n for n in A014847. - _Reinhard Zumkeller_
%C A071416 a(n) = gcd(n, C(n)), C(n) the Catalan numbers. - _Peter Luschny_ Oct 06 2011
%H A071416 T. D. Noe, <a href="/A071416/b071416.txt">Table of n, a(n) for n = 1..1000</a>
%H A071416 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CentralBinomialCoefficient.html">Central Binomial Coefficient</a>
%e A071416 a(10) = gcd(10, binomial(20, 10)) = gcd(10, 184756) = 2.
%t A071416 Table[GCD[n,Binomial[2n,n]],{n,100}] (* _Harvey P. Dale_, Nov 10 2011 *)
%Y A071416 Cf. A000984, A000108.
%K A071416 nonn,nice
%O A071416 1,2
%A A071416 _Reinhard Zumkeller_, May 29 2002