A245908 - OEIS

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A245908

The number of distinct prime factors of prime(n)^2-1.

1, 1, 2, 2, 3, 3, 2, 3, 3, 4, 3, 3, 4, 4, 3, 3, 4, 4, 4, 4, 3, 4, 4, 4, 3, 4, 4, 3, 4, 4, 3, 5, 4, 5, 4, 4, 4, 3, 4, 4, 4, 5, 4, 3, 4, 4, 5, 4, 4, 5, 4, 5, 4, 4, 3, 4, 4, 4, 4, 5, 4, 4, 5, 5, 4, 4, 5, 4, 4, 5, 4, 4, 4, 5, 5, 3, 5, 4, 4, 5

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OFFSET

1,3

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A082863(prime(n)).

a(n) = A008334(n) + A008335(n) - 1, if n>1.

MAPLE

A245908 := proc(n)

A082863(ithprime(n)) ;

end proc:

MATHEMATICA

Table[PrimeNu[Prime[n]^2 - 1], {n, 100}] (* Wesley Ivan Hurt, Aug 05 2014 *)

PROG

(PARI) vector(100, n, omega(prime(n)^2-1)) \\ Derek Orr, Aug 05 2014

(Magma) [#PrimeDivisors(NthPrime(n)^2 -1): n in [1..100]]; // Vincenzo Librandi, Apr 27 2019

CROSSREFS

Cf. A008334, A008335, A082863.

Sequence in context: A110012 A233542 A375802 * A023514 A179751 A373888

Adjacent sequences: A245905 A245906 A245907 * A245909 A245910 A245911

KEYWORD

nonn

AUTHOR

R. J. Mathar, Aug 05 2014

STATUS

approved