[seqfan] primes beginning 101 in binary

Neil Sloane njasloane at gmail.com
Sat Sep 19 16:10:51 CEST 2015

Alois has produced a clean binary version of A089755 and A262283, namely
a(1) = 2. For n>1, let s denote the binary string of a(n-1) with the
leftmost 1 and following consecutive 0's removed. Then a(n) is the smallest
prime not yet present whose binary representation begins with s.

This led me to look at "primes beginning 101 in binary" etc.:
Primes whose binary expansion begins with binary expansion of 1, 2, 3, 4,
5, 6, 7: A000040, A080165, A080166, A262286, A262284, A262287, A262285.

My question is, is it known that any of these sequences are infinite (other
than A000040, the primes themselves)?

Is there a proof that the new sequence A262350 or its complement are

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