OFFSET
1,1
COMMENTS
A000005(a(n)) = A001221(a(n)) + A001222(a(n)); prime powers are a subsequence (A000961); complement of A102467; not the same as A085156.
Equals { n | omega(n)=1 or Omega(n)=2 }, that is, these are exactly the prime powers (>1) and semiprimes. - M. F. Hasler, Jan 14 2008
For n > 1: A086971(a(n)) <= 1. - Reinhard Zumkeller, Dec 14 2012
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
MAPLE
with(numtheory):
q:= n-> is(tau(n)=bigomega(n)+nops(factorset(n))):
select(q, [$1..200])[]; # Alois P. Heinz, Jul 14 2023
MATHEMATICA
Select[Range[110], DivisorSigma[0, #]==PrimeOmega[#]+PrimeNu[#]&] (* Harvey P. Dale, Mar 09 2016 *)
PROG
(Sage)
def is_A102466(n) :
def A102466_list(n) :
return [k for k in (1..n) if is_A102466(k)]
A102466_list(109) # Peter Luschny, Feb 08 2012
(Haskell)
a102466 n = a102466_list !! (n-1)
a102466_list = [x | x <- [1..], a000005 x == a001221 x + a001222 x]
-- Reinhard Zumkeller, Dec 14 2012
(PARI) is(n)=my(f=factor(n)[, 2]); #f==1 || f==[1, 1]~ \\ Charles R Greathouse IV, Oct 19 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jan 09 2005
STATUS
approved