OFFSET
1,1
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
Will Nicholes Prime Signatures
OEIS Wiki, Numbers with same prime signature.
MAPLE
a:= proc(n) option remember; local k;
for k from 1+ `if` (n=1, 1, a(n-1))
while sort (map (x-> x[2], ifactors(k)[2]), `>`)<>[7, 1, 1]
do od; k
end:
seq (a(n), n=1..40); # Alois P. Heinz, Jan 23 2011
MATHEMATICA
f[n_]:=Sort[Last/@FactorInteger[n]]=={1, 1, 7}; Select[Range[30000], f]
PROG
(PARI) list(lim)=my(v=List(), t1, t2); forprime(p=2, (lim\6)^(1/7), t1=p^7; forprime(q=2, lim\t1, if(p==q, next); t2=t1*q; forprime(r=q+1, lim\t2, if(p==r, next); listput(v, t2*r)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jul 20 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Jul 24 2010
EXTENSIONS
Title edited by Daniel Forgues, Jan 22 2011
STATUS
approved