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

1,2

Links

Table of n, a(n) for n=1..20.

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 *)

Crossrefs

Sequence in context: A203121 A232220 A129653 * A117927 A143340 A151379

Adjacent sequences: A081719 A081720 A081721 * A081723 A081724 A081725

Keyword

nonn

Author

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

Status

approved