OFFSET
1,1
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
60 is in the sequence because it is not squarefree and it is divisible by three distinct primes: 2, 3, 5.
72 is not in the sequence, because although it is not squarefree, it is divisible by only two distinct primes: 2 and 3.
MATHEMATICA
nsD3Q[n_] := Block[{fi = FactorInteger@ n}, Length@ fi == 3 && Plus @@ Last /@ fi > 3]; Select[ Range@ 494, nsD3Q] (* Robert G. Wilson v, Feb 09 2012 *)
Select[Range[500], PrimeNu[#] == 3 && PrimeOmega[#] > 3 &] (* Alonso del Arte, Mar 23 2015, based on a comment from Robert G. Wilson v, Feb 09 2012; requires Mathematica 7.0+ *)
PROG
(PARI) is_A178212(n)={ omega(n)==3 & bigomega(n)>3 }
for(n=1, 999, is_A178212(n) & print1(n", ")) \\ M. F. Hasler, Feb 09 2012
(Haskell)
a178212 n = a178212_list !! (n-1)
a178212_list = filter f [1..] where
f x = length (a027748_row x) == 3 && any (> 1) (a124010_row x)
-- Reinhard Zumkeller, Apr 03 2015
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, May 24 2010
STATUS
approved