OFFSET
1,1
COMMENTS
Complement to A115392.
FORMULA
a(n) ~ n. - Charles R Greathouse IV, Jul 02 2017
MATHEMATICA
sp=Select[Range[4, 1000], 2==PrimeOmega[#]&]; Flatten[Position[Mod[sp, 2], 1]]
PROG
(PARI) lista(nn) = vsp = select(x->(bigomega(x)==2), vector(nn, k, k)); select(x->(x%2), vsp, 1); \\ Michel Marcus, Jul 02 2017
(Python)
from math import isqrt
from sympy import primepi, primerange
def A289182(n):
def iterfun(f, n=0):
m, k = n, f(n)
while m != k: m, k = k, f(k)
return m
def f(x): return int(-((t:=primepi(s:=isqrt(x)))*(t-1)>>1)+sum(primepi(x//p) for p in primerange(3, s+1)))
return f(m:=iterfun(lambda x:int(n+x-f(x)), n))+primepi(m>>1) # Chai Wah Wu, Apr 03 2025
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Jun 27 2017
STATUS
approved