OFFSET
2,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 2..73
EXAMPLE
a(2) = 5 divides 1 + 2^2 ;
a(3) = 2 divides 1 + 2^2 + 3^3 = 32 ;
a(4) = 3 divides 1 + 2^2 + 3^3 + 4^4 = 288 = 2^5*3^2 ;
a(5) = 3413 divides 1 + 2^2 + 3^3 + 4^4 + 5^5 = 3413.
a(13) = 3514531963 divides 1 + 2^2 + 3^3 + ... + 13^13 = 88799 * 3514531963.
MAPLE
with (numtheory):
s:= proc(n) option remember; `if`(n=1, 1, s(n-1)+n^n) end:
a:= n-> max(factorset(s(n))[]):
seq (a(n), n=2..23); # Alois P. Heinz, Jul 24 2012
MATHEMATICA
s = 1; Table[s = s + n^n; FactorInteger[s][[-1, 1]], {n, 2, 24}] (* T. D. Noe, Jul 25 2012 *)
Module[{nn=30, lst}, lst=Table[n^n, {n, nn}]; Table[FactorInteger[Total[Take[lst, k]]][[-1, 1]], {k, 2, nn}]] (* Harvey P. Dale, Oct 09 2022 *)
PROG
(PARI) a(n) = vecmax(factor(sum(k=1, n, k^k))[, 1]); \\ Michel Marcus, Feb 09 2020
(Magma) [Max(PrimeDivisors(&+[k^k:k in [1..n]])):n in [2..23]]; // Marius A. Burtea, Feb 09 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jul 24 2012
STATUS
approved