

A182597


Number of prime factors of form cn+1 for numbers 5^n+1


0



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

2,5


COMMENTS

Repeated prime factors are counted.


LINKS

Table of n, a(n) for n=2..107.
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=11, 5^n+1=48828126=2*3*23*67*5281 has three prime factors of form, namely 23=2n+1, 67=6n+1, 5281=480n+1. Thus a(11)=3.


MATHEMATICA

m = 5; n = 2; nmax = 107;
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}]
Table[{p, e}=Transpose[FactorInteger[5^n+1]]; Sum[If[Mod[p[[i]], n] == 1, e[[i]], 0], {i, Length[p]}], {n, 2, 50}]


CROSSREFS

Sequence in context: A151931 A185636 A333212 * A290491 A194314 A006371
Adjacent sequences: A182594 A182595 A182596 * A182598 A182599 A182600


KEYWORD

nonn


AUTHOR

Seppo Mustonen, Nov 24 2010


STATUS

approved



