

A182594


Number of prime factors of form cn+1 for numbers 7^n1


0



1, 1, 2, 1, 2, 2, 1, 3, 3, 2, 2, 1, 4, 2, 3, 2, 4, 2, 3, 1, 4, 3, 4, 3, 3, 4, 4, 3, 3, 3, 2, 4, 3, 3, 3, 3, 4, 4, 5, 3, 4, 2, 4, 2, 4, 2, 3, 4, 4, 5, 5, 3, 5, 1, 6, 3, 4, 4, 5, 4, 6, 2, 3, 6, 6, 4, 6, 3, 8, 2, 5, 5, 5, 3, 2, 3, 7, 2, 5
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OFFSET

2,3


LINKS

Table of n, a(n) for n=2..80.
S. Mustonen, On prime factors of numbers m^n+1


EXAMPLE

For n=9, 7^n1=40353606=2*3^3*19*37*1063 has three prime factors of form, namely 19=2n+1, 37=6n+1, 1063=118n+1. Thus a(9)=3.


MATHEMATICA

m = 7; n = 2; nmax = 80;
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

Sequence in context: A173306 A276430 A325002 * A201593 A029287 A055184
Adjacent sequences: A182591 A182592 A182593 * A182595 A182596 A182597


KEYWORD

nonn


AUTHOR

Seppo Mustonen, Nov 22 2010


STATUS

approved



