OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..3000
EXAMPLE
The first term having more than 2 prime powers is 105468750 = 2^1 * 3^3 * 5^9, not shown.
MATHEMATICA
q[n_] := Module[{e = FactorInteger[n][[;; , 2]]}, Length[e] > 1 && e == 3^Range[0, Length[e]-1]]; Select[Range[10^5], q] (* Amiram Eldar, Jun 29 2024 *)
PROG
(PARI) geoprog(n, m) = { local(a, x, j, nf, fl=0); for(x=1, n, a=factor(x); nf=omega(x); for(j=1, nf, if(a[j, 2]==3^(j-1), fl=1, fl=0; break); ); if(fl&nf>1, print1(x", ")) ) }
(PARI) is(n) = if(n == 1 || isprime(n), 0, my(e = factor(n)[, 2]); for(i = 1, #e, if(e[i] != 3^(i-1), return(0))); 1); \\ Amiram Eldar, Jun 29 2024
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Feb 27 2005
STATUS
approved