A104297 a(n) = prime((a(n-1) + 1)/2), a(1)=21.

21, 31, 53, 103, 239, 659, 2213, 8887, 42473, 240151, 1584607, 12069311, 105036509, 1034651039, 11438277847, 142253144233, 1946420671121, 29165259660989

Offset

1,1

Comments

All primes except a(1) which is any odd integer; a(1)=21 the least integer missing in A104296 and A104298.

Links

Table of n, a(n) for n=1..18.

Mathematica

a[1] = 21; a[n_] := a[n] = Prime[(a[n - 1] + 1)/2]; Table[ a[n], {n, 18}] (* Robert G. Wilson v, Mar 24 2005 *)

Crossrefs

Cf. A104296, A104298, A104299, A104300, A104301, A104302, A104303, A104304.

Sequence in context: A113762 A032585 A138822 * A106324 A208293 A032013

Adjacent sequences: A104294 A104295 A104296 * A104298 A104299 A104300

Keyword

easy,nonn

Author

Zak Seidov, Mar 20 2005

Extensions

a(14)-a(18) from Robert G. Wilson v, Mar 24 2005

Status

approved