A340821 - OEIS

%I #7 Jan 23 2021 19:02:39

%S 3,3,3,61,3,3,17,3,5,13,3,29,17,13,3,5,7,19,23,5,11,3,3,23,3,3,3,19,

%T 19,7,7,23,43,5,7,67,7,7,11,19,29,3,3,7,19,5,3,3,23,3,29,7,17,13,37,

%U 13,7,3,23,3,3,19,53,29,17,3,3,43,7,43,5,11,5,7,19,19,19,163,3,3,3,7,5,31,17,19

%N a(n) is the least prime p such that prime(n)*p + prime(n+1)*q + prime(n+2)*r is prime where p,q,r are consecutive primes.

%H Robert Israel, <a href="/A340821/b340821.txt">Table of n, a(n) for n = 2..10000</a>

%e a(3) = 3 where 5*3 + 7*5 + 11*7 = 167 is prime.

%p f:= proc(n) local k,t;

%p   for k from 1 do

%p      t:=ithprime(n)*ithprime(k) + ithprime(n+1)*ithprime(k+1) + ithprime(n+2)*ithprime(k+2);

%p      if isprime(t) then return ithprime(k) fi;

%p   od

%p end proc:

%p map(f, [$2..100]);

%Y Cf. A340817.

%K nonn

%O 2,1

%A _J. M. Bergot_ and _Robert Israel_, Jan 22 2021