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 A081722 #9 Nov 02 2017 12:02:51
%S A081722 1,4,15,83,561,6332,88086,1561008,31966485,746278033,19441692751,
%T A081722 559268543516,17599832876941,601468320356528,22182618618501188,
%U A081722 878172760660077348,37144096971415045713,1671734397769302244110,79770632874353931073165,4022719642533206402716726
%N A081722 Row sums of triangle in A081720.
%t A081722 t[n_, k_] := (For[t1 = 0; d = 1, d <= n, d++, If[Mod[n, d] == 0, t1 = t1 + EulerPhi[d]*k^(n/d)]]; If[EvenQ[n], (t1 + (n/2)*(1+k)*k^(n/2))/(2*n), (t1 + n*k^((n+1)/2))/(2*n)]); a[n_] := Sum[t[n, k], {k, 1, n}]; Array[a, 20] (* _Jean-François Alcover_, Nov 02 2017, after Maple code for A081720 *)
%K A081722 nonn
%O A081722 1,2
%A A081722 _N. J. A. Sloane_, based on information supplied by _Gary W. Adamson_, Apr 05 2003