A139758 a(n) is the smallest prime such that (a(n) - the n-th prime) is a power of 2.

3, 5, 7, 11, 13, 17, 19, 23, 31, 31, 47, 41, 43, 47, 79, 61, 61, 317, 71, 73, 89, 83, 211, 97, 101, 103, 107, 109, 113, 241, 131, 139, 139, 1163, 151, 167, 173, 167, 199, 181, 181, 197, 193, 197, 199, 263, 227, 227, 229, 233, 241, 241, 257, 283, 769, 271, 271

Offset

1,1

Comments

It is only conjectured (see Cino Hilliard's comment at A094076) that this sequence is defined for all n.

Links

Table of n, a(n) for n=1..57.

Formula

a(n) = A000040(n) + 2^A094076(n). - R. J. Mathar, May 20 2008

Maple

A094076 := proc(n) local k, p ; k := 0 ; p := ithprime(n) ; while not isprime(p+2^k) do k := k+1 ; od: k ; end: A139758 := proc(n) ithprime(n)+2^A094076(n) ; end: seq(A139758(n), n=1..80) ; # R. J. Mathar, May 20 2008

Mathematica

sp2[n_]:=Module[{p=Prime[n], k}, k=NextPrime[p]; While[!IntegerQ[Log[2, k-p]], k=NextPrime[k]]; k]; Array[sp2, 60] (* Harvey P. Dale, Dec 27 2019 *)

Crossrefs

Cf. A094076, A033875.

Sequence in context: A120637 A278454 A064534 * A306084 A060770 A246568

Adjacent sequences: A139755 A139756 A139757 * A139759 A139760 A139761

Keyword

nonn

Author

Leroy Quet, May 19 2008

Extensions

More terms from R. J. Mathar, May 20 2008

Status

approved