OFFSET
1,1
COMMENTS
These are numbers that a naïve factoring algorithm can declare done at the penultimate prime factor.
LINKS
Marc Moskowitz, Table of n, a(n) for n = 1..10000
MATHEMATICA
cnQ[n_]:=Module[{pfs=Flatten[Table[#[[1]], #[[2]]]&/@FactorInteger[n]]}, CompositeQ[ n]&&Last[pfs]<pfs[[-2]]^2]; Select[Range[200], cnQ] (* Harvey P. Dale, Nov 05 2017 *)
PROG
(PARI) is(n)=my(f=factor(n), e=#f~); e && (f[e, 2]>1 || (e>1 && f[e-1, 1]^2>f[e, 1])) \\ Charles R Greathouse IV, Feb 19 2016
(Python)
seq = []
for n in range(2, 1000):
temp = n
factor = 2
while temp > 1:
if temp % factor == 0:
temp //= factor
if temp == 1:
continue
if temp < factor * factor:
seq.append(n)
else:
factor += 1
print(seq)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Marc Moskowitz, Feb 19 2016
STATUS
approved