OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
1711710 = 2 * 3^2 * 5 * 7 * 11 * 13 * 19.
MATHEMATICA
Select[Range[9!, 5*9! ], Length[FactorInteger[ # ]]==7&]
Select[Range[144*10^4], PrimeNu[#]==7&] (* Harvey P. Dale, Jul 05 2022 *)
PROG
(PARI) isA176655(n)=omega(n)==7 \\ Charles R Greathouse IV, Mar 11 2011
(PARI) (PARI) A246655(lim)=my(v=List(primes([2, lim\=1]))); for(e=2, logint(lim, 2), forprime(p=2, sqrtnint(lim, e), listput(v, p^e))); Set(v)
list(lim, pr=7)=if(pr==1, return(A246655(lim))); my(v=List(), pr1=pr-1, mx=prod(i=1, pr1, prime(i))); forprime(p=prime(pr), lim\mx, my(u=list(lim\p, pr1)); for(i=1, #u, listput(v, p*u[i]))); Set(v) \\ Charles R Greathouse IV, Feb 03 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Apr 22 2010
STATUS
approved