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 A056821 #18 Sep 08 2022 08:45:01
%S A056821 1,6,22,36,104,382,712,1936,4320,6824,15012,46992,79344,183000,421008,
%T A056821 480000,1453784,4658784,8877792,20958480,38887680,61284600,110250264,
%U A056821 388201176,719023536,1734432480,2889658368,4745378304,10350643968,32212254718,66251144568
%N A056821 Totient of the Woodall numbers (A003261), n*2^n -1.
%H A056821 Amiram Eldar, <a href="/A056821/b056821.txt">Table of n, a(n) for n = 1..853</a> (terms 1..150 from Vincenzo Librandi)
%F A056821 a(n) = A000010(A003261(n)).
%p A056821 a:= n-> numtheory[phi](n*2^n-1):
%p A056821 seq(a(n), n=1..35); # _Alois P. Heinz_, Apr 15 2019
%t A056821 Table[EulerPhi[n 2^n - 1], {n, 1, 35}]
%o A056821 (Magma) [EulerPhi(n*2^n-1): n in [1..30]]; // _Vincenzo Librandi_, Apr 15 2019
%o A056821 (PARI) a(n) = eulerphi(n*2^n -1); \\ _Michel Marcus_, Apr 15 2019
%Y A056821 Cf. A000010, A003261.
%K A056821 nonn
%O A056821 1,2
%A A056821 _Robert G. Wilson v_, Aug 31 2000