A254616 - OEIS

%I #6 Feb 25 2015 12:34:06

%S 3,6,9,30,33,36,38,54,66,89,92,93,98,121,125,128,154,155,167,189,198,

%T 231,291,296,300,310,323,334,345,357,373,407,436,437,444,456,481,483,

%U 492,493,515,516,541,554,581,628,649,681,713,714,749,750,809,818,826,834,864,868,872,881,888

%N Let i < k and prime(k) == x(i) mod prime(i). This sequence gives the indices k of the primes prime(k) such that Sum(i=1..k-1, x(i)) is prime.

%e prime(3) is 5, 5 == 1 mod 2 == 2 mod 3. 1 + 2 = 3, which is prime. Therefore, the index of the prime(3) is in the sequence.

%t lst1={};lst2={};i=1;primes=Prime[Range[1000]];

%t Do[

%t    While[i<k,AppendTo[lst1,Mod[primes[[k]],primes[[i]]]];i++];

%t    If[PrimeQ[Total[lst1]],AppendTo[lst2,k]];

%t    i=1;lst1={},

%t    {k,3,Length[primes]}

%t ];

%t lst2

%Y Cf. A000040.

%K easy,nonn

%O 1,1

%A _Ivan N. Ianakiev_, Feb 03 2015