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A036335
Total number of composite numbers with n digits and n prime factors (counted with multiplicity).
4
0, 31, 225, 1563, 10222, 63030, 374264, 2160300, 12196405, 67724342, 371233523, 2014305995
OFFSET
1,2
COMMENTS
Essentially the same as A124033.
LINKS
Carlos Rivera, Puzzle 25. Composed primes (by G.L. Honaker, Jr.), The Prime Puzzles and Problems Connection. (A related puzzle.)
EXAMPLE
a(1) = 0, since any single-digit number with 1 prime factor is a prime!
MATHEMATICA
Table[Total[Table[If[CompositeQ[n]&&PrimeOmega[n]==x, 1, 0], {n, 10^(x-1), 10^x-1}]], {x, 8}] (* The program generates the first 8 terms of the sequence. *) (* Harvey P. Dale, Jun 19 2022 *)
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Patrick De Geest, Dec 15 1998
EXTENSIONS
One more term from Naohiro Nomoto, Jul 31 2001
a(9)-a(12) from Ray Chandler, Apr 12 2011
STATUS
approved