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 A209429 #12 Jan 03 2018 15:55:28
%S A209429 1,2,8,11,71,268,2302,2771,29543,172654,2194624,7533469,111102841,
%T A209429 875654984,1335478594,16332117629,307026528761,3040884758542,
%U A209429 63303287929996,345404844856129,7886534621278669,94005382576044068,2335627560917144282,7547413632563686237,11923476834093824801
%N A209429 Numerator of l(n), where l(1)=1, l(2)=2, l(n)=l(n-1)+2*l(n-2)/n.
%D A209429 Szekeres, G. The average value of skew Hadamard matrices. Proceedings of the First Australian Conference on Combinatorial Mathematics (Univ. Newcastle, Newcastle, 1972), pp. 55--59. Univ. of Newcastle Res. Associates, Newcastle, 1972. MR0349708 (50 #2201)
%H A209429 G. C. Greubel, <a href="/A209429/b209429.txt">Table of n, a(n) for n = 1..500</a>
%e A209429 1, 2, 8/3, 11/3, 71/15, 268/45, 2302/315, 2771/315, 29543/2835, 172654/14175, 2194624/155925, 7533469/467775, 111102841/6081075, 875654984/42567525, ...
%t A209429 Numerator[RecurrenceTable[{a[1] == 1, a[2] == 2, a[n] == a[n - 1] + (2 a[n - 2])/n}, a, {n, 50}]] (* _G. C. Greubel_, Jan 02 2018 *)
%Y A209429 Cf. A209430, A052127.
%K A209429 nonn,frac
%O A209429 1,2
%A A209429 _N. J. A. Sloane_, Mar 22 2012