OFFSET
1,4
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = |{j < n : omega(j) = omega(n)}|.
a(n) = A067003(n) - 1.
EXAMPLE
a(12) = 2 because omega(12) = 2 and also omega(6) = omega(10) = 2.
MAPLE
R:= NULL:
for n from 1 to 100 do
w:= nops(numtheory:-factorset(n));
if assigned(V[w]) then V[w]:= V[w]+1 else V[w]:= 1 fi;
R:= R, V[w]-1
od:
R; # Robert Israel, Feb 25 2024
MATHEMATICA
Table[Length[Select[Range[n - 1], PrimeNu[#] == PrimeNu[n] &]], {n, 80}]
PROG
(PARI) a(n)={my(t=omega(n)); sum(k=1, n-1, omega(k)==t)} \\ Andrew Howroyd, Oct 31 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Oct 31 2020
STATUS
approved