A103797 - OEIS

%I #3 Mar 31 2012 10:23:47

%S 2,3,7,9,11,21,27,29,31,39,41,47,51,53,55,61,63,67,71,81,89,91,107,

%T 113,121,123,129,131,135,139,143,149,151,157,159,163,169,175,179,183,

%U 187,191,197,199,207,211,217,223,235,241,251,259,261,269,279,281,287,295

%N Indices of n such that A019565(n)-1 is prime.

%e A019565(0)=1, 1-1=0 is not prime;

%e A019565(1)=2, 2-1=1 is not prime;

%e A019565(2)=3, 3-1=2 is prime, so a(1)=2.

%t A019565 = Function[tn, k1 = tn; o = 1; tt = 1; While[k1 > 0, k2 = Mod[k1, 2]; If[k2 == 1, tt = tt*Prime[o]]; k1 = (k1 - k2)/2; o = o + 1]; tt]; Do[cp = A019565[n] - 1; If[PrimeQ[cp], Print[n]], {n, 0, 1000}]

%Y Cf. A019565, A103796.

%K nonn

%O 0,1

%A _Lei Zhou_, Feb 22 2005