A117675 - OEIS

%I #15 Jul 23 2024 03:10:57

%S 9,11,13,20,23,29,47,64,70,88,121,126,145,148,153,174,190,195,201,213,

%T 223,245,294,298,320,337,369,381,429,436,445,462,486,495,504,536,548,

%U 584,596,608,639,677,747,819,827,831,868,877,887,902,905,970

%N Numbers k such that prime(k) + prime(k+1) + prime(k+2) is prime and also there is a j such that prime(j) + prime(j+1) + prime(j+2) = prime(k).

%o (PARI)

%o isok2(k)={my(q=prime(k), p=q\3); while(p>2, p=precprime(p-1); my(p2=nextprime(p+1), t=p+p2+nextprime(p2+1)); if(t<=q, return(t==q))); 0}

%o isok(k)={my(p1=prime(k), p2=nextprime(p1+1), p3=nextprime(p2+1)); isprime(p1+p2+p3) && isok2(k)}

%o select(isok, [1..1000]) \\ _Andrew Howroyd_, Jul 23 2024

%Y Cf. A109756, A072225.

%K nonn

%O 1,1

%A _Roger L. Bagula_, Apr 12 2006

%E Edited and more terms from _Andrew Howroyd_, Jul 23 2024