OFFSET
1,2
COMMENTS
a(n) is even for n > 1.
a(n) = 2 for n in A340225.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
For n=3, prime(3)=5, prime(4)=7, prime(5)=11, and 6*5+7= 37 and 6*5+11=41 are prime, so a(3)=6.
MAPLE
f:= proc(n) local p, q, r, k;
p:= ithprime(n);
q:= ithprime(n+1);
r:= ithprime(n+2);
for k from 2 by 2 do
if isprime(k*p+q) and isprime(k*p+r) then return k fi
od
end proc:
f(1):= 1:
map(f, [$1..100]);
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Dec 31 2020
STATUS
approved