OFFSET
1,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
385=5*7*11; 5,7 and 11 are safe primes.
MATHEMATICA
lst={}; Do[If[Plus@@Last/@FactorInteger[n]==3, a=Length[First/@FactorInteger[n]]; If[a==3, b=First/@FactorInteger[n]; c=b[[1]]; d=b[[2]]; e=b[[3]]; If[PrimeQ[(c-1)/2]&&PrimeQ[(d-1)/2]&&PrimeQ[(e-1)/2], AppendTo[lst, n]]]], {n, 7!}]; lst
PROG
(PARI) list(lim)=my(v=List(), P=select(p->isprime(p\2), primes([5, sqrtint(lim\5+1)-1])), p, q, t); for(i=1, #P, p=P[i]; if(p^3>=lim, break); for(j=i+1, #P, q=P[j]; t=p*q; forprime(r=q+4, lim\t, if(isprime(r\2), listput(v, r*t))))); Set(v); \\ Charles R Greathouse IV, Oct 14 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vladimir Joseph Stephan Orlovsky, Feb 27 2009
STATUS
approved