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editing
approved
PrimeOmega[Range[80]!!] (* Harvey P. Dale, May 29 2015 *)
approved
editing
Jeff Burch (gburch(AT)erols.com)
<a href="/Sindx_index/Fa.html#factorial">Index entries for sequences related to factorial numbers</a>
<a href="/Sindx_Fa.html#factorial">Index entries for sequences related to factorial numbers</a>
nonn,easy,new
<a href="http://www.research.att.com/~njas/sequences/Sindx_Fa.html#factorial">Index entries for sequences related to factorial numbers</a>
nonn,easy,new
<a href="http://www.research.att.com/~njas/sequences/Sindx_FFa.html#factorial">Index entries for sequences related to factorial numbers</a>
nonn,easy,new
Jeff Burch (gburch@(AT)erols.com)
Number of prime factors of double factorials n!! (A006882), with multiplicity.
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
1,4
<a href="http://www.research.att.com/~njas/sequences/Sindx_F.html#factorial">Index entries for sequences related to factorial numbers</a>
8!!=8*6*4*2=2^3*2*3*2^2*2=2^7*3. Eight prime factors, so a(8)=8.
nonn,easy
Jeff Burch (gburch@erols.com)
approved