A124387 Largest prime < 2*a(n-1) written in binary, a(1)=2.

10, 11, 101, 111, 1101, 10111, 101011, 1010011, 10100011, 100111101, 1001110111, 10011101011, 100111000111, 1001110001011, 10011011110101, 100110111100001, 1001101110111101, 10011011101010011, 100110111010011101, 1001101110100011111, 10011011101000111011

Offset: 1

Author

Artur Jasinski, Dec 16 2006

Keywords

• nonn

Crossrefs

Cf. A006992, A007088, A126031.

Programs

Mathematica

NestList[FromDigits[IntegerDigits[NextPrime[FromDigits[IntegerDigits[ 2#], 2],-1],2]]&,10,20] (* Harvey P. Dale, Sep 26 2015 *)

Formula

a(n) = A007088(A006992(n)).

Extensions

Corrected and extended by Harvey P. Dale, Sep 26 2015