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A340694
a(n) is the first prime p such that p*2^n+q*3^n is prime, where q is the prime following p.
2
2, 2, 5, 2, 5, 5, 7, 7, 5, 19, 7, 7, 5, 103, 7, 5, 7, 37, 5, 7, 31, 7, 211, 5, 197, 7, 17, 23, 7, 5, 5, 67, 17, 7, 7, 19, 127, 7, 7, 11, 7, 29, 79, 167, 79, 43, 89, 101, 17, 127, 89, 17, 137, 173, 71, 31, 73, 163, 67, 5, 11, 211, 31, 109, 67, 13, 7, 199, 97, 137, 109, 263, 107, 5, 101, 17, 283
OFFSET
0,1
LINKS
EXAMPLE
a(2) = 5 because 5*2^2+7*3^2 = 83 is prime, while 3*2^2+5*3^2 = 57 and 2*2^2+3*3^2 = 35 are not.
MAPLE
f:= proc(n) local p, q;
q:= 2;
do
p:= q; q:= nextprime(q);
until isprime(p*2^n+q*3^n);
p
end proc:
map(f, [$0..100]);
PROG
(PARI) a(n) = my(p=2, q=nextprime(p+1)); while(! isprime(p*2^n+q*3^n), p=q; q=nextprime(p+1)); p; \\ Michel Marcus, Jan 21 2021
CROSSREFS
Sequence in context: A171868 A292146 A334685 * A101910 A162784 A093660
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Jan 20 2021
STATUS
approved