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 A056229 #7 Feb 21 2025 17:48:06
%S A056229 1,1,0,-4,64,-240,-2656,15360,-88064,-1714176,-28506112,59061248,
%T A056229 1975595008,-107448238080,858018086912,12209125720064,61138306793472,
%U A056229 -297002777247744,-7586668200067072,309144292445913088,-20518123014457393152,-58844751529044344832,2248491526894557069312
%N A056229 Hankel transform of Euler totient function (A000010).
%t A056229 a[n_]:=Det[Table[EulerPhi[i+j-1], {i, n}, {j, n}]]; Join[Array[a, 23]] (* _Stefano Spezia_, Feb 21 2025 *)
%Y A056229 See A001906 for definition of Hankel transform.
%K A056229 sign
%O A056229 1,4
%A A056229 _N. J. A. Sloane_, Aug 06 2000
%E A056229 a(21)-a(23) from _Stefano Spezia_, Feb 21 2025