cp's OEIS Frontend

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

%I A124403 #7 Sep 08 2022 08:45:28
%S A124403 0,7,55,493,5698,82199,1419759,28501115,651233660,16676686695,
%T A124403 472883843991,14705395791305,497538872883726,18193397941038735,
%U A124403 714950006521386975,30046260016074301943,1344648068888240941016
%N A124403 a(n) = -1 + Sum_{i=1..n} Sum_{j=1..n} i^j.
%C A124403 p divides a(p-2) for prime p>2. p^k divides a(p^k-2) for prime p>2.
%H A124403 G. C. Greubel, <a href="/A124403/b124403.txt">Table of n, a(n) for n = 1..385</a>
%F A124403 a(n) = -1 + Sum_{i=1..n} Sum_{j=1..n} i^j.
%F A124403 a(n) = n - 1 + Sum_{j=2..n} j*(j^n - 1)/(j-1).
%F A124403 a(n) = A086787(n) - 1.
%p A124403 seq( n-1+add(j*(j^n-1)/(j-1), j=2..n), n=1..30); # _G. C. Greubel_, Dec 25 2019
%t A124403 Table[Sum[i^j,{i,1,n},{j,1,n}]-1,{n,1,25}]
%o A124403 (PARI) vector(30, n, n-1 + sum(j=2,n, j*(j^n-1)/(j-1)) ) \\ _G. C. Greubel_, Dec 25 2019
%o A124403 (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
%o A124403 (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
%o A124403 (GAP) List([1..30], n-> n-1 + Sum([2..n], j-> j*(j^n-1)/(j-1)) ); # _G. C. Greubel_, Dec 25 2019
%Y A124403 Cf. A086787.
%K A124403 nonn
%O A124403 1,2
%A A124403 _Alexander Adamchuk_, Dec 14 2006