A168475 - OEIS

%I #5 Apr 29 2018 21:38:02

%S 107,163,233,271,359,521,719,733,839,1129,1187,1231,1693,1733,1777,

%T 1847,1871,2053,2137,2287,2423,2543,2593,2677,2719,2843,2897,3217,

%U 3229,3257,3491,3623,3659,3853,4019,4027,4219,4231,4243,4441,4591,4679,4751,4903

%N Primes of the form: sum of 3 consecutive products of two distinct primes.

%H Robert Israel, <a href="/A168475/b168475.txt">Table of n, a(n) for n = 1..10000</a>

%e 34 + 35 + 38 = 107, 51 + 55 + 57 = 163,..

%p N:= 5000: # to get terms where the three consecutive terms all < N

%p Primes:= select(isprime, [2, seq(2*k+1, k=1..floor(N/2))]):

%p L:= sort(convert({seq(seq(p*q, q=Primes[1..ListTools:-BinaryPlace(Primes, N/p)]), p=Primes)} minus {seq(p^2, p=Primes)},list)):

%p select(isprime, [seq(L[i]+L[i+1]+L[i+2], i=1..nops(L)-2)]); # _Robert Israel_, Apr 29 2018

%t f[n_]:=Last/@FactorInteger[n]=={1,1}; a=6;b=10;lst={};Do[If[f[n],p=a+b+n;If[PrimeQ[p],AppendTo[lst,p]];a=b;b=n],{n,13,7!}];lst

%Y Cf. A006881, A168474

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Nov 26 2009