This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A124077 #6 Oct 27 2024 01:36:24
%S A124077 3,5,7,29,73,2131,4211
%N A124077 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 A124077 A072762(4211) tested as PRP, others certified primes.
%C A124077 A072762(4211) is prime. a(8) > 200000. - _Jason Yuen_, Oct 26 2024
%e A124077 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 A124077 F[j_] := PrimeQ[Numerator[ Sum[ 1/2^Prime[k], {k, 1, j} ] ]] ; Prime[Select[Range[600], F]]
%Y A124077 Cf. A072762, A010051.
%K A124077 hard,nonn,more,base
%O A124077 1,1
%A A124077 Anton Vrba (antonvrba(AT)yahoo.com), Nov 24 2006