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A046799 Number of distinct prime factors of 2^n+1. 4
1, 1, 1, 1, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 3, 3, 1, 2, 4, 2, 2, 3, 3, 2, 3, 4, 4, 3, 2, 3, 5, 2, 2, 4, 4, 5, 4, 3, 4, 3, 2, 3, 6, 2, 3, 5, 5, 3, 3, 3, 5, 5, 3, 3, 6, 5, 3, 4, 3, 4, 4, 2, 5, 5, 2, 6, 6, 3, 3, 4, 6, 3, 5, 3, 5, 6, 4, 6, 9, 2, 3, 6, 5, 6, 5, 4, 5, 4, 4, 4, 10, 6, 2, 4, 4, 5, 3, 5, 6, 7, 6, 2, 9, 3, 2 (list; graph; refs; listen; history; internal format)
OFFSET

0,6

COMMENTS

The length of row n in A060444.

LINKS

T. D. Noe, Table of n, a(n) for n=0..500

FORMULA

a[ n ] = Length[ FactorInteger [ 2^n + 1 ] ]

EXAMPLE

a[ 7 ]=129=3.43 has 2 prime factors

CROSSREFS

A000051.

Cf. A086257 (number of primitive prime factors)

Sequence in context: A129139 A032539 A122922 * A037809 A097195 A129451

Adjacent sequences:  A046796 A046797 A046798 * A046800 A046801 A046802

KEYWORD

nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu)

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Last modified February 15 04:23 EST 2012. Contains 205694 sequences.