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 A112093 #13 Jan 05 2025 19:51:38
%S A112093 0,3,13,197,1105,9211,130277,82987349,331950131,16929464521,
%T A112093 29241805241,3538258509761,6259995854281,1057939300471201,
%U A112093 1057939300716589,51133732870640471,372975463296151087,107789908892879155343,51058377896658637853,681986753565766904623961
%N A112093 Numerator of 3*Sum_{i=1..n} 1/(i^2*C(2*i,i)).
%H A112093 Robert Israel, <a href="/A112093/b112093.txt">Table of n, a(n) for n = 0..772</a>
%H A112093 C. Elsner, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Papers1/43-1/paper43-1-5.pdf">On recurrence formulas for sums involving binomial coefficients</a>, Fib. Q., 43,1 (2005), 31-45.
%F A112093 3*Sum_{i >= 1} 1/(i^2*C(2*i, i)) = zeta(2) = Pi^2/6.
%p A112093 0, 3/2, 13/8, 197/120, 1105/672, 9211/5600, 130277/79200, 82987349/50450400, ... -> Pi^2/6.
%p A112093 X:= [0,seq(3/(i^2*binomial(2*i,i)),i=1..20)]:
%p A112093 S:= ListTools:-PartialSums(X):
%p A112093 map(numer,S); # _Robert Israel_, Apr 08 2019
%o A112093 (PARI) a(n) = numerator(3*sum(i=1, n, 1/(i^2*binomial(2*i, i)))); \\ _Michel Marcus_, Mar 10 2016
%Y A112093 Cf. A112094.
%K A112093 nonn,frac
%O A112093 0,2
%A A112093 _N. J. A. Sloane_, Nov 30 2005