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A124874 Number of primes dividing A007408(n). +0
1
0, 1, 1, 3, 2, 3, 3, 2, 3, 4, 3, 2, 3, 2, 1, 3, 2, 4, 1, 3, 2, 5, 2, 4, 2, 1, 3, 4 (list; graph; listen)
OFFSET

1,4

EXAMPLE

a(1) = 0 since no prime divides A007408(1)=1,

a(2) = 1 since 3 is the only prime dividing A007408(2)=9,

a(3) = 1 since A007408(3)=251 is prime,

a(4) = 3 since A007408(4)=5 x 11 x 37,

a(6) = 3 since 7,11,53 are the only primes dividing A007408(6)=7^2 x 11 x 53.

MAPLE

seq( (nops@op)(2, (ifactors@A007408)(n)), n=1..25);

CROSSREFS

Cf. A007408, A124876, A124877.

Sequence in context: A153092 A165601 A054263 this_sequence A016459 A060585 A114451

Adjacent sequences: A124871 A124872 A124873 this_sequence A124875 A124876 A124877

KEYWORD

hard,nonn

AUTHOR

M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Nov 11 2006

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Last modified December 10 00:48 EST 2009. Contains 170565 sequences.


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