A122462 - OEIS

%I #2 Mar 30 2012 17:27:49

%S 2,2,3,3,3,2,5,5,3,2,2,7,7,3,2,11,11,3,3,2,2,13,13,3,2,17,17,3,2,5,5,

%T 7,2,19,19,3,5,2,23,23,3,2,2,2,2,11,5,2,29,29,3,7,7,2,31,31,3,2,13,5,

%U 2,2,37,37,3,3,3,2,2,41,41,3,3,7,11,2,43,43,3,2,2,47,47,3,2,2,5,5,5,2,2,2

%N a(n) = gcd(b(n-1),b(n)), where b(i) = A122280(i).

%C Primes arising in A122280 as greatest common divisor.

%o (PARI) {m=100;z=2*m;w=vectorsmall(z);b=1;a=2;w[b]=1;w[a]=1;stop=0;n=3;while(!stop&&n<=m,j=1;while(j<=z&&(w[j]==1||!isprime(p=gcd(a,j))),j++);if(j>z,stop=1,print1(p,",");a=j;w[a]=1;n++))}

%Y Cf. A122280.

%K nonn

%O 3,1

%A _Klaus Brockhaus_, Sep 09 2006