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A325403 Number of permutations of the multiset of prime factors of 2n whose first part is not 2. 1
0, 0, 1, 0, 1, 1, 1, 0, 2, 1, 1, 1, 1, 1, 4, 0, 1, 3, 1, 1, 4, 1, 1, 1, 2, 1, 3, 1, 1, 6, 1, 0, 4, 1, 4, 4, 1, 1, 4, 1, 1, 6, 1, 1, 9, 1, 1, 1, 2, 3, 4, 1, 1, 6, 4, 1, 4, 1, 1, 8, 1, 1, 9, 0, 4, 6, 1, 1, 4, 6, 1, 5, 1, 1, 9, 1, 4, 6, 1, 1, 4, 1, 1, 8, 4, 1, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,9

LINKS

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

FORMULA

a(n) = A008480(2n) - A008480(n) = A325392(2n).

EXAMPLE

The a(60) = 8 permutations of {2,2,2,3,5} whose first part is not 2:

  3 2 2 2 5

  3 2 2 5 2

  3 2 5 2 2

  3 5 2 2 2

  5 2 2 2 3

  5 2 2 3 2

  5 2 3 2 2

  5 3 2 2 2

MATHEMATICA

Table[Length[Select[Permutations[Flatten[Table@@@FactorInteger[2*n]]], First[#]!=2&]], {n, 100}]

CROSSREFS

Cf. A008480, A056239, A112798, A325327, A325362, A325364, A325367, A325390, A325392, A325407.

Sequence in context: A218220 A247487 A010248 * A132068 A173441 A326851

Adjacent sequences:  A325400 A325401 A325402 * A325404 A325405 A325406

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 02 2019

STATUS

approved

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Last modified November 13 20:57 EST 2019. Contains 329106 sequences. (Running on oeis4.)