A124403 a(n) = -1 + Sum_{i=1..n} Sum_{j=1..n} i^j.

0, 7, 55, 493, 5698, 82199, 1419759, 28501115, 651233660, 16676686695, 472883843991, 14705395791305, 497538872883726, 18193397941038735, 714950006521386975, 30046260016074301943, 1344648068888240941016

Offset: 1

Author

Alexander Adamchuk, Dec 14 2006

Keywords

• nonn

Comments

p divides a(p-2) for prime p>2. p^k divides a(p^k-2) for prime p>2.

Links

• G. C. Greubel, Table of n, a(n) for n = 1..385

Crossrefs

Cf. A086787.

Programs

GAP

List([1..30], n-> n-1 + Sum([2..n], j-> j*(j^n-1)/(j-1)) ); # G. C. Greubel, Dec 25 2019

Magma

[0] cat [n-1 + (&+[j*(j^n-1)/(j-1): j in [2..n]]): n in [2..30]]; // G. C. Greubel, Dec 25 2019

Maple

seq( n-1+add(j*(j^n-1)/(j-1), j=2..n), n=1..30); # G. C. Greubel, Dec 25 2019

Mathematica

Table[Sum[i^j,{i,1,n},{j,1,n}]-1,{n,1,25}]

PARI

vector(30, n, n-1 + sum(j=2,n, j*(j^n-1)/(j-1)) ) \\ G. C. Greubel, Dec 25 2019

Sage

[n-1 + sum(j*(j^n-1)/(j-1) for j in (2..n)) for n in (1..30)] # G. C. Greubel, Dec 25 2019

Formula

a(n) = -1 + Sum_{i=1..n} Sum_{j=1..n} i^j.

a(n) = n - 1 + Sum_{j=2..n} j*(j^n - 1)/(j-1).

a(n) = A086787(n) - 1.