A122250 Partial sums of A004128.

0, 1, 3, 7, 12, 18, 26, 35, 45, 58, 72, 87, 104, 122, 141, 162, 184, 207, 233, 260, 288, 318, 349, 381, 415, 450, 486, 526, 567, 609, 653, 698, 744, 792, 841, 891, 944, 998, 1053, 1110, 1168

Offset: 0

Author

Paul Barry, Aug 27 2006

Keywords

• easy
• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 0..1000

Programs

Mathematica

Table[Sum[Sum[Floor[3*j/3^k], {k, 1, j}], {j, 0, n}], {n, 0, 50}] (* G. C. Greubel, May 14 2017 *)

PARI

for(n=0,50, print1(sum(j=0,n, sum(k=0,j, floor(j/3^k))), ", ")) \\ G. C. Greubel, May 14 2017

Formula

G.f.: (1/(1-x))*Sum{k=0..infinity} ( x^(3^k)/((1-x)*(1-x^(3^k))) ).

a(n) = Sum_{j=0..n} ( Sum_{k=0..j} floor(j/3^k) ).