A055011 a(n+1) = next smallest prime beginning with a(n) when written in binary, starting with 2.

2, 5, 11, 23, 47, 191, 383, 3067, 12269, 196307, 6281839, 50254717, 201018869, 804075479, 1608150959, 102921661397, 1646746582367, 13173972658937, 105391781271503, 210783562543007, 3372537000688127, 26980296005505019, 863369472176160611, 6906955777409284889

Offset: 0

Author

Henry Bottomley, May 31 2000

Keywords

• base
• easy
• nonn

Comments

a(5)=191 because a(4)=47 which in binary is 101111, none of 1011110(94) 1011111(95) 10111100(188) 10111101(189) 10111110 (190) are prime, but 10111111(191) is.

Crossrefs

Cf. A048549 for base 10 analog.

A055011, A261200 and A261201 are all essentially the same sequence.

Programs

Haskell

a055011 n = a055011_list !! n
a055011_list = iterate a208241 2  -- Reinhard Zumkeller, Feb 14 2013

Maple

A055011 := proc(n)
    option remember;
    if n = 0 then
        2 ;
    else
        A208241(procname(n-1)) ;
    end if;
end proc: # R. J. Mathar, May 06 2017

Formula

a(n+1) = A208241(a(n)). - Reinhard Zumkeller, Feb 14 2013