OFFSET
1,1
COMMENTS
A014613 is completely determined by A030514, A065036, A085986, A085987 and A046386 since p(4) = 5. (cf. A000041). More generally, the first term of sequences which completely determine the k-almost primes can be found in A036035 (a resorted version of A025487).
A050326(a(n)) = 4. - Reinhard Zumkeller, May 03 2013
EXAMPLE
a(1) = 60 since 60 = 2*2*3*5 and has three distinct prime factors.
MATHEMATICA
f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 2}; Select[Range[2000], f] (* Vladimir Joseph Stephan Orlovsky, May 03 2011 *)
pefp[{a_, b_, c_}]:={a^2 b c, a b^2 c, a b c^2}; Module[{upto=800}, Select[ Flatten[ pefp/@Subsets[Prime[Range[PrimePi[upto/6]]], {3}]]//Union, #<= upto&]] (* Harvey P. Dale, Oct 02 2018 *)
PROG
(PARI) list(lim)=my(v=List(), t, x, y, z); forprime(p=2, lim^(1/4), t=lim\p^2; forprime(q=p+1, sqrtint(t), forprime(r=q+1, t\q, x=p^2*q*r; y=p*q^2*r; listput(v, x); if(y<=lim, listput(v, y); z=p*q*r^2; if(z<=lim, listput(v, z)))))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 15 2011
(PARI) is(n)=vecsort(factor(n)[, 2]~)==[1, 1, 2] \\ Charles R Greathouse IV, Oct 19 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Alford Arnold, Jul 08 2003
EXTENSIONS
More terms from Reinhard Zumkeller, Jul 25 2003
STATUS
approved