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A178646 a(n) = product of divisors d of n such that d^k is not equal to n for any k >= 1. 1
1, 1, 1, 1, 1, 6, 1, 4, 1, 10, 1, 144, 1, 14, 15, 8, 1, 324, 1, 400, 21, 22, 1, 13824, 1, 26, 9, 784, 1, 27000, 1, 512, 33, 34, 35, 46656, 1, 38, 39, 64000, 1, 74088, 1, 1936, 2025, 46, 1, 5308416, 1, 2500 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Table of n, a(n) for n=1..50.

FORMULA

a(n) = A007955(n) / A157068 (n).

a(1) = 1, a(p) = 1, a(pq) = 1, a(pq...z) = (pq…z)^2((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 = 16, set of such divisors is {1, 8}; a(16) = 1*8=8.

PROG

(Sage) A178646 = lambda n: prod(d for d in divisors(n) if not n.is_power_of(d)) # [D. S. McNeil, Dec 28 2010]

CROSSREFS

Sequence in context: A101023 A195303 A160199 * A144540 A292107 A212037

Adjacent sequences:  A178643 A178644 A178645 * A178647 A178648 A178649

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Dec 25 2010

STATUS

approved

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Last modified July 28 19:33 EDT 2021. Contains 346335 sequences. (Running on oeis4.)