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A183102 a(n) = product of powerful divisors d of n. 4
1, 1, 1, 4, 1, 1, 1, 32, 9, 1, 1, 4, 1, 1, 1, 512, 1, 9, 1, 4, 1, 1, 1, 32, 25, 1, 243, 4, 1, 1, 1, 16384, 1, 1, 1, 1296, 1, 1, 1, 32, 1, 1, 1, 4, 9, 1, 1, 512, 49, 25, 1, 4, 1, 243, 1, 32, 1, 1, 1, 4, 1, 1, 9, 1048576, 1, 1, 1, 4, 1, 1, 1, 746496, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

a(n) = product of divisors d of n from set A001694 - powerful numbers.

Sequence is not the same as A183104(n): a(72) = 746496, A183104(72) = 10368.

Not multiplicative: a(4)*a(9) = 4*9=36 <> a(36) = 1296. - R. J. Mathar, Jun 07 2011

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16385

FORMULA

a(n) = A007955(n) / A183103(n).

a(1) = 1, a(p) = 1, a(pq) = 1, a(pq...z) = 1, a(p^k) = p^((1/2*k*(k+1))-1), for p, q = primes, k = natural numbers, pq...z = product of k (k > 2) distinct primes p, q, ..., z.

EXAMPLE

For n = 12, set of such divisors is {1, 4}; a(12) = 1*4 = 4.

MAPLE

isA001694 := proc(n) for p in ifactors(n)[2] do if op(2, p) = 1 then return false; end if; end do; return true; end proc:

A183102 := proc(n) local a, d; a := 1 ; for d in numtheory[divisors](n) do if isA001694(d) then a := a*d; end if; end do; a ; end proc:

seq(A183102(n), n=1..70) ; # R. J. Mathar, Jun 07 2011

PROG

(PARI) A183102(n) = { my(m=1); fordiv(n, d, if(ispowerful(d), m *= d)); m; }; \\ Antti Karttunen, Oct 07 2017

CROSSREFS

Cf. A001694, A007955, A183097, A183103, A183104.

Sequence in context: A265679 A112622 A183104 * A178649 A119591 A304876

Adjacent sequences:  A183099 A183100 A183101 * A183103 A183104 A183105

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Dec 25 2010

STATUS

approved

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Last modified February 21 03:02 EST 2020. Contains 332086 sequences. (Running on oeis4.)