A063487 - OEIS

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A063487

Number of distinct prime divisors of 2^(2^n)-1 (A051179).

0, 1, 2, 3, 4, 5, 7, 9, 11, 13, 16, 20, 25

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OFFSET

0,3

COMMENTS

2^(2^n)-1 is the product of the first n Fermat numbers F(0),...,F(n-1) (A000215). Hence this sequence is just the summation of A046052, which gives the number of prime factors in each Fermat number. - T. D. Noe, Jan 07 2003

REFERENCES

D. M. Burton, Elementary Number Theory, Allyn and Bacon Inc., Boston MA, 1976, p. 238.

LINKS

Table of n, a(n) for n=0..12.

Eric Weisstein's World of Mathematics, Fermat Number

PROG

(PARI) for(n=0, 22, print(omega(2^(2^n)-1)))

CROSSREFS

Cf. A051179, A000215, A046052.

Sequence in context: A158923 A008740 A089651 * A253063 A081998 A325266

Adjacent sequences: A063484 A063485 A063486 * A063488 A063489 A063490

KEYWORD

nonn

AUTHOR

Jason Earls, Jul 28 2001

EXTENSIONS

More terms from T. D. Noe, Jan 07 2003

STATUS

approved