A157354 Products of 3 distinct safe primes.

385, 805, 1265, 1645, 1771, 2065, 2585, 2905, 3245, 3619, 3745, 4543, 4565, 5405, 5845, 5885, 6265, 6391, 6785, 7567, 7945, 8239, 9185, 9205, 9499, 9545, 9845, 11891, 12145, 12305, 12485, 12565, 12859, 13363, 13405, 13783, 13865, 14465, 14927

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

Subsequence of A007304.

Cf. A001358, A005384, A005385, A006881, A111206, A157342, A157344, A157345, A157346, A157347, A157352, A157353

Sequence in context: A152941 A229853 A317272 * A200525 A225711 A351696

Adjacent sequences: A157351 A157352 A157353 * A157355 A157356 A157357

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, Feb 27 2009

Status

approved