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 A047680 #25 Nov 30 2022 08:01:08 %S A047680 1,28,342736,29398976,22841912576,495449389339648,113828913905979392, %T A047680 4138783908783021080576,226044736813811127599528869888, %U A047680 35882867158508587149623987273728,5564179808875681941887049052192768,197363311803624016534960016288517315362816 %N A047680 a(n) = 2^(2*n-2) * (2^(2*n-1)-1) * numerator(|Bernoulli(4*n)|/n). %H A047680 <a href="/index/Be#Bernoulli">Index entries for sequences related to Bernoulli numbers</a> %p A047680 (-1)*2^(2*n-2)*(2^(2*n-1)-1)*numer(bernoulli(4*n)/n); %o A047680 (PARI) a(n) = 2^(2*n-2) * (2^(2*n-1)-1) * numerator(abs(bernfrac(4*n))/n); \\ _Michel Marcus_, Nov 30 2022 %Y A047680 Cf. A189995 (similar formula). %K A047680 nonn %O A047680 1,2 %A A047680 _N. J. A. Sloane_ %E A047680 Edited by _Andrey Zabolotskiy_, Nov 30 2022