A064988 Multiplicative with a(p^e) = prime(p)^e.

1, 3, 5, 9, 11, 15, 17, 27, 25, 33, 31, 45, 41, 51, 55, 81, 59, 75, 67, 99, 85, 93, 83, 135, 121, 123, 125, 153, 109, 165, 127, 243, 155, 177, 187, 225, 157, 201, 205, 297, 179, 255, 191, 279, 275, 249, 211, 405, 289, 363, 295, 369, 241, 375, 341, 459, 335, 327

Offset: 1

Author

Vladeta Jovovic, Oct 30 2001

Keywords

• mult
• nonn

Examples

			a(12) = a(2^2*3) = prime(2)^2 * prime(3) = 3^2*5 = 45, where prime(n) = A000040(n).
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..20000
• Index entries for sequences computed from indices in prime factorization (first 1000 terms from Harry J. Smith)

Crossrefs

Cf. A000040, A003961, A003963 (a left inverse), A006450, A048767, A257538, A290641.

Cf. A076610 (terms sorted into ascending order).

Programs

Maple

a:= n-> mul(ithprime(i[1])^i[2], i=ifactors(n)[2]):
seq(a(n), n=1..70);  # Alois P. Heinz, Sep 06 2018

Mathematica

Table[If[n == 1, 1, Apply[Times, FactorInteger[n] /. {p_, e_} /; p > 1 :> Prime[p]^e]], {n, 58}] (* Michael De Vlieger, Aug 22 2017 *)

PARI

{ for (n=1, 1000, f=factor(n)~; a=1; for (i=1, length(f), a*=prime(f[1, i])^f[2, i]); write("b064988.txt", n, " ", a) ) } \\ Harry J. Smith, Oct 02 2009

PARI

a(n) = {my(f = factor(n)); for (k=1, #f~, f[k, 1] = prime(f[k, 1]);); factorback(f);} \\ Michel Marcus, Aug 08 2017

Python

from sympy import factorint, prime
from operator import mul
def a(n): return 1 if n==1 else reduce(mul, [prime(p)**e for p, e in factorint(n).items()])
print([a(n) for n in range(1, 101)]) # Indranil Ghosh, Aug 08 2017

Scheme

(define (A064988 n) (if (= 1 n) n (* (A000040 (A020639 n)) (A064988 (A032742 n))))) ;; Antti Karttunen, Aug 08 2017

Formula

From Antti Karttunen, Aug 08 & 22 2017: (Start)

For n = p_{i1} * p_{i2} * ... * p_{ik}, where the indices i1, i2, ..., ik of primes p are not necessarily distinct, a(n) = A006450(i1) * A006450(i2) * ... * A006450(ik).

a(n) = A003961(A290641(n)).

A046523(a(n)) = A046523(n). [Preserves the prime signature of n].

A003963(a(n)) = n.

(End)