OFFSET
1,1
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
Will Nicholes, Prime Signatures
EXAMPLE
120=2^3*3*5, 168=2^3*3*7, 180=2^2*3^2*5, 252=2^2*3^2*7, 264=2^3*3*11, 270=2*3^3*5
MATHEMATICA
f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 3} || Sort[Last/@FactorInteger[n]]=={1, 2, 2}; Select[Range[2000], f]
PROG
(PARI) list(lim)=my(v=List(), t); forprime(p=2, (lim\6)^(1/3), forprime(q=2, sqrt(lim\p^3), if(p==q, next); t=p^3*q; forprime(r=q+1, lim\t, if(p==r, next); listput(v, t*r)))); forprime(p=2, sqrt(lim\12), forprime(q=p+1, sqrt(lim\p^2\2), t=(p*q)^2; forprime(r=2, lim\t, if(p==r||q==r, next); listput(v, t*r)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 19 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Jul 21 2010
STATUS
approved