The On-Line Encyclopedia of Integer Sequences (OEIS)

A368039 revision #5

A368039

The product of exponents of prime factorization of the nonsquarefree numbers.

2, 3, 2, 2, 4, 2, 2, 3, 2, 3, 2, 5, 4, 3, 2, 2, 4, 2, 2, 2, 3, 3, 2, 2, 6, 2, 6, 2, 2, 4, 4, 2, 3, 2, 2, 5, 2, 2, 4, 3, 6, 4, 2, 2, 3, 2, 2, 3, 2, 7, 2, 3, 3, 2, 8, 2, 2, 2, 3, 2, 2, 5, 4, 2, 3, 2, 2, 2, 2, 4, 4, 3, 2, 3, 6, 4, 2, 6, 2, 2, 4, 2, 9, 2, 5, 4, 2

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OFFSET

1,1

COMMENTS

The terms of A005361 that are larger than 1, since A005361(k) = 1 if and only if k is squarefree (A005117).

LINKS

Table of n, a(n) for n=1..87.

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A005361(A013929(n)).

Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = ((zeta(2)*zeta(3)/zeta(6)) - 1/zeta(2))/(1-1/zeta(2)) = (A082695 - A059956)/A229099 = 3.406686208821... .

MATHEMATICA

Select[Table[Times @@ FactorInteger[n][[;; , 2]], {n, 1, 250}], # > 1 &]

PROG

(PARI) lista(kmax) = {my(p); for(k = 1, kmax, p = vecprod(factor(k)[, 2]); if(p > 1, print1(p, ", "))); }

CROSSREFS

Cf. A005117, A005361, A013929.

Cf. A084936, A174961, A275699, A368038, A368040.

Cf. A059956, A082695, A229099.

Sequence in context: A375342 A368713 A375341 * A160558 A241019 A023581

Adjacent sequences: A368036 A368037 A368038 * A368040 A368041 A368042

KEYWORD

nonn

AUTHOR

Amiram Eldar, Dec 09 2023

STATUS

reviewed