A128997 - OEIS

%I #3 Mar 31 2012 13:48:30

%S 11,12,15,20,21,22,23,24,25,28,29,30,33,35,36,37,39,40,41,42,43,44,45,

%T 46,47,48,50,51,52,53,55,56,57,58,59,60,63,64,65,66,67,68,69,70,71,72,

%U 73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,90,91,92,93,94,95,96

%N indices k such that A063670(k) differs from A005420(k).

%C Primes in this sequence are those for which A005420(n) < 2^n-1, i.e. 2^n-1 is not prime.

%o (PARI) t=1;vector(100,i,until( A063670(t++) != A005420(t),);t)

%Y Cf. A005420, A063670.

%K nonn

%O 1,1

%A _M. F. Hasler_, Apr 30 2007