A140366 - OEIS

%I #6 Jan 26 2021 10:48:14

%S 1,3,3,3,1,2,3,3,1,1,2,3,2,3,1,0,3,3,3,0,0,3,1,2,1,2,2,3,1,1,2,1,3,2,

%T 0,2,0,3,3,1,2,1,1,1,1,2,3,2,1,0,0,3,3,0,0,2,2,1,3,1

%N a(n) = isprime(6n-1) + 2*isprime(6n-5), where isprime = A010051.

%C The idea is to consider 2-bit words, where the least resp. most significant bit correspond to primality of the respective member in the couple (6n-1,6n-5). (It might have been more natural to inverse the correspondences, i.e. to associate the LSB to the smaller number of the pair.) - _M. F. Hasler_, Jun 16 2008

%o (PARI) a(n)=isprime(6*n-5)<<1+isprime(6*n-1) \\ _M. F. Hasler_, Jun 16 2008

%Y Cf. A002476, A007528.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Jun 10 2008

%E Edited by _M. F. Hasler_, Jun 16 2008