%I #6 Oct 27 2024 01:36:24

%S 3,5,7,29,73,2131,4211

%N Indices of the primes in A072762; b(i=a(n)) is prime, b(i) coded as binary word of length=i with k-th bit set iff k is prime (1<=k<=i).

%C A072762(4211) tested as PRP, others certified primes.

%C A072762(4211) is prime. a(8) > 200000. - _Jason Yuen_, Oct 26 2024

%e a(3)=7 as A072762(7)=53 and 53 is prime! Also, the binary concatenation of the first a(n) terms of A010051 is prime. E.g. the first 7 term concatenation is binary 0110101 = decimal 53 and is prime!

%t F[j_] := PrimeQ[Numerator[ Sum[ 1/2^Prime[k], {k, 1, j} ] ]] ; Prime[Select[Range[600], F]]

%Y Cf. A072762, A010051.

%K hard,nonn,more,base

%O 1,1

%A Anton Vrba (antonvrba(AT)yahoo.com), Nov 24 2006