1,6

It seems that every prime p > 3 can be expressed as 2*p1 + 3*p2, where p1, p2 are primes or 1. I have tested it for the first 1500 primes (up to 12553) and it is true.

Table of n, a(n) for n=1..58.

a(11)=2 because we can write 31 (the 11th prime) as 2* 5 + 3* 7 OR 2* 11 + 3* 3

a(12)=3 because we can write 37 (the 12th prime) as 2* 2 + 3* 11 OR 2* 11 + 3* 5 OR 2* 17 + 3* 1

Sequence in context: A030603 A092670 A210528 * A127238 A072114 A090621

Adjacent sequences: A120447 A120448 A120449 * A120451 A120452 A120453

nonn

Vassilis Papadimitriou, Jul 20 2006

approved