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 A037239 #29 Jul 02 2025 16:01:56
%S A037239 8,16,8,32,8,16,8,64,8,16,8,32,8,16,8,128,8,16,8,32,8,16,8,64,8,16,8,
%T A037239 32,8,16,8,256,8,16,8,32,8,16,8,64,8,16,8,32,8,16,8,128,8,16,8,32,8,
%U A037239 16,8,64,8,16,8,32,8,16,8,512,8,16,8,32,8,16,8,64,8
%N A037239 Numerator of Pi^(2n)/(GAMMA(2n)*(1-2^(-2n))*Zeta(2n)); = 8*(highest power of 2 dividing n).
%H A037239 Antti Karttunen, <a href="/A037239/b037239.txt">Table of n, a(n) for n = 1..16384</a>
%H A037239 Harvey Cohn, <a href="http://dx.doi.org/10.1090/S0002-9904-1965-11343-X">Some elementary aspects of modular functions in several variables</a>, Bull. Amer. Math. Soc. 71 (1965), 681-704, (esp. p. 688).
%p A037239 with(numtheory): for n from 1 to 200 do if n mod 2 = 1 then printf(`%d,`,8) else printf(`%d,`,8*2^ifactors(n)[2][1][2]) fi; od:
%p A037239 seq(2^(3+padic[ordp](n,2)), n=1..73); # _Peter Luschny_, Apr 03 2014
%t A037239 a[n_] := 8*BitAnd[n, -n]; Table[a[n], {n, 1, 81}] (* _Jean-François Alcover_, Sep 20 2011, after _Joerg Arndt_ *)
%o A037239 (PARI) a(n)=if(n<1,0,8*2^valuation(n,2))
%o A037239 (Magma) [2^(3 + Valuation(n,2)): n in [1..80]]; // _G. C. Greubel_, Nov 01 2018
%Y A037239 Equals 8*A006519. Denominators given by A002425.
%K A037239 nonn,frac,easy
%O A037239 1,1
%A A037239 _N. J. A. Sloane_
%E A037239 More terms from _James Sellers_, Jun 20 2000