OFFSET
2,4
LINKS
Seppo Mustonen, Table of n, a(n) for n = 2..170
S. Mustonen, On prime factors of numbers m^n+-1
Seppo Mustonen, On prime factors of numbers m^n+-1 [Local copy]
EXAMPLE
For n=6, 3^n-1=728 has two prime factors of the form cn+1, namely 7=n+1 and 13=2n+1. Thus a(6)=2.
MATHEMATICA
m = 3; n = 2; nmax = 170;
While[n <= nmax, {l = FactorInteger[m^n - 1]; s = 0;
For[i = 1, i <= Length[l],
i++, {p = l[[i, 1]];
If[IntegerQ[(p - 1)/n] == True, s = s + l[[i, 2]]]; }];
a[n] = s; } n++; ];
Table[a[n], {n, 2, nmax}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Seppo Mustonen, Nov 22 2010
STATUS
approved