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A322837
Number of positive integers less than n with fewer distinct prime factors than n.
5
0, 1, 1, 1, 1, 5, 1, 1, 1, 8, 1, 9, 1, 10, 10, 1, 1, 12, 1, 13, 13, 13, 1, 14, 1, 15, 1, 16, 1, 29, 1, 1, 19, 19, 19, 19, 1, 20, 20, 20, 1, 40, 1, 22, 22, 22, 1, 23, 1, 24, 24, 24, 1, 25, 25, 25, 25, 25, 1, 57, 1, 27, 27, 1, 28, 62, 1, 29, 29, 65, 1, 30, 1, 31
OFFSET
1,6
LINKS
David A. Corneth, PARI program
EXAMPLE
Column n lists the a(n) positive integers less than n with fewer distinct prime factors than n:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
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1 1 1 1 5 1 1 1 9 1 11 1 13 13 1 1 17 1 19
4 8 9 11 11 16 17
3 7 8 9 9 13 16
2 5 7 8 8 11 13
1 4 5 7 7 9 11
3 4 5 5 8 9
2 3 4 4 7 8
1 2 3 3 5 7
1 2 2 4 5
1 1 3 4
2 3
1 2
1
MATHEMATICA
Table[Length[Select[Range[n], PrimeNu[#]<PrimeNu[n]&]], {n, 100}]
PROG
(PARI) \\ See Corneth link
CROSSREFS
Positions of 1's are A246655.
Sequence in context: A367202 A292771 A369364 * A348978 A168677 A345939
KEYWORD
nonn,easy
AUTHOR
Gus Wiseman, Dec 28 2018
STATUS
approved