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A045766 Number of prime factors of double factorials n!! (A006882), with multiplicity. 0
0, 1, 1, 3, 2, 5, 3, 8, 5, 10, 6, 13, 7, 15, 9, 19, 10, 22, 11, 25, 13, 27, 14, 31, 16, 33, 19, 36, 20, 39, 21, 44, 23, 46, 25, 50, 26, 52, 28, 56, 29, 59, 30, 62, 33, 64, 34, 69, 36, 72, 38, 75, 39, 79, 41, 83, 43, 85, 44, 89, 45, 91, 48, 97, 50, 100, 51, 103, 53, 106, 54, 111 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..72.

Index entries for sequences related to factorial numbers

EXAMPLE

8!!=8*6*4*2=2^3*2*3*2^2*2=2^7*3. Eight prime factors, so a(8)=8.

MATHEMATICA

PrimeOmega[Range[80]!!] (* Harvey P. Dale, May 29 2015 *)

CROSSREFS

Sequence in context: A075889 A181771 A238628 * A281668 A132817 A131025

Adjacent sequences: A045763 A045764 A045765 * A045767 A045768 A045769

KEYWORD

nonn,easy

AUTHOR

Jeff Burch

STATUS

approved

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Last modified November 28 03:39 EST 2022. Contains 358406 sequences. (Running on oeis4.)