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 A144028 #13 May 18 2018 08:41:37
%S A144028 1,1,-1,-6,-7,3,36,55,-9,-221,-373,-18,1290,2506,643,-7488,-16487,
%T A144028 -7258,42577,106701,65695,-236923,-681856,-534130,1282512,4304675,
%U A144028 4079414,-6687222,-26866199,-29871373,33019148,165771711,212092381,-149113958,-1010995614
%N A144028 INVERT transform of A055615, n*mu(n).
%C A144028 Equals row sums of triangle A144029.
%H A144028 Alois P. Heinz, <a href="/A144028/b144028.txt">Table of n, a(n) for n = 0..2000</a>
%F A144028 a(4) = -7 = (0, -3, -2, 1) dot (1, 1, -1, -6); where (0, -3, -2, 1) = the first 4 terms of n*mu(n) reversed. (1, 1, -1, -6) = the first 4 terms of the INVERT recursion operation.
%p A144028 a:= proc(n) option remember; `if`(n=0, 1,
%p A144028 add(a(n-i)*i*numtheory[mobius](i), i=1..n))
%p A144028 end:
%p A144028 seq(a(n), n=0..40); # _Alois P. Heinz_, Sep 22 2017
%t A144028 a[n_] := a[n] = If[n == 0, 1, Sum[a[n-i]*i*MoebiusMu[i], {i, 1, n}]];
%t A144028 Table[a[n], {n, 0, 40}] (* _Jean-François Alcover_, May 18 2018, translated from Maple *)
%Y A144028 Cf. A055615, A144029.
%K A144028 sign
%O A144028 0,4
%A A144028 _Gary W. Adamson_, Sep 07 2008
%E A144028 Corrected from a(9) onwards by _R. J. Mathar_, Jan 27 2011
%E A144028 a(0)=1 prepended by _Alois P. Heinz_, Sep 22 2017