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A307734 Smallest k such that the adjusted frequency depth of k! is n, and 0 if there is no such k. 1
1, 2, 0, 3, 4, 5, 7, 26, 65, 942, 24147 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The adjusted frequency depth of a positive integer n is 0 if n = 1, and otherwise it is 1 plus the number of times one must apply A181819 to reach a prime number, where A181819(k = p^i*...*q^j) = prime(i)*...*prime(j) = product of primes indexed by the prime exponents of k. For example, 180 has adjusted frequency depth 5 because we have: 180 -> 18 -> 6 -> 4 -> 3.

Conjecture: this sequence has infinitely many nonzero terms.

LINKS

Table of n, a(n) for n=0..10.

EXAMPLE

Column n is the sequence of images under A181819 starting with a(n)!:

  -  2  -  6  24  120  5040  403291461126605635584000000

           4  10  20   84    11264760

           3  4   6    12    240

              3   4    6     28

                  3    4     6

                       3     4

                             3

CROSSREFS

Essentially the same as A325410.

a(n) is zero or the first position of n in A325272.

Cf. A000142, A323023, A325238, A325273, A325274, A325275, A325276, A325277, A325416.

Omega-sequence statistics: A001222 (first omega), A001221 (second omega), A071625 (third omega), A323022 (fourth omega), A304465 (second-to-last omega), A182850 or A323014 (length/frequency depth), A325248 (Heinz number), A325249 (sum).

Sequence in context: A173517 A109921 A139637 * A243202 A257136 A258871

Adjacent sequences:  A307731 A307732 A307733 * A307735 A307736 A307737

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Apr 25 2019

STATUS

approved

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Last modified January 27 05:36 EST 2021. Contains 340455 sequences. (Running on oeis4.)