A081722 Row sums of triangle in A081720.

1, 4, 15, 83, 561, 6332, 88086, 1561008, 31966485, 746278033, 19441692751, 559268543516, 17599832876941, 601468320356528, 22182618618501188, 878172760660077348, 37144096971415045713, 1671734397769302244110, 79770632874353931073165, 4022719642533206402716726

Offset: 1

Author

N. J. A. Sloane, based on information supplied by Gary W. Adamson, Apr 05 2003

Keywords

• nonn

Programs

Mathematica

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 *)