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 A106478 #9 Nov 16 2024 02:57:28
%S A106478 1,-1,1,-1,-1,1,1,-1,-1,1,-1,1,-1,-1,1,3,-1,1,-1,-1,1,-3,3,-1,1,-1,-1,
%T A106478 1,-1,-3,3,-1,1,-1,-1,1,7,-1,-3,3,-1,1,-1,-1,1,-9,7,-1,-3,3,-1,1,-1,
%U A106478 -1,1,5,-9,7,-1,-3,3,-1,1,-1,-1,1,-1,5,-9,7,-1,-3,3,-1,1,-1,-1,1,-7,-1,5,-9,7,-1,-3,3,-1,1,-1,-1,1,25,-7,-1,5,-9,7,-1,-3,3,-1,1,-1,-1,1
%N A106478 Inverse of sequence array for Euler phi function.
%C A106478 Row sums are A106480. Sequence matrix for A106479.
%F A106478 Riordan array (1/Sum_{j>=0}, phi(j+1) x^j, x).
%e A106478 Triangle begins:
%e A106478 1;
%e A106478 -1, 1;
%e A106478 1, -1, -1, 1;
%e A106478 -1, 1, -1, -1, 1;
%e A106478 3, -1, 1, -1, -1, 1;
%e A106478 -3, 3, -1, 1, -1, -1, 1;
%e A106478 -1, -3, 3, -1, 1, -1, -1, 1;
%e A106478 ...
%t A106478 T[n_, k_] := If[k <= n, EulerPhi[n - k + 1], 0]; With[{max = 14}, Tinv = Inverse[Table[T[n, k], {n, 0, max - 1}, {k, 0, max - 1}]]; Table[Tinv[[n, k]], {n, 1, max}, {k, 1, n}] // Flatten] (* _Amiram Eldar_, Nov 16 2024 *)
%Y A106478 Cf. A000010 (phi), A106476, A106477, A106479, A106480.
%K A106478 easy,sign,tabl
%O A106478 0,16
%A A106478 _Paul Barry_, May 03 2005