A192495 Smallest prime p such that there is a gap of phi(n) between p and next prime.

2, 2, 3, 3, 7, 3, 23, 7, 23, 7, 139, 7, 199, 23, 89, 89, 1831, 23, 523, 89, 199, 139, 1129, 89, 887, 199, 523, 199, 2971, 89, 4297, 1831, 887, 1831, 1669, 199, 9551, 523, 1669, 1831, 19333, 199, 16141, 887, 1669, 1129, 81463, 1831, 16141

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..1360

Formula

a(n) = A000230(phi(n)/2) for n >= 3. - Robert Israel, Jan 10 2017

Example

a(9) = 23  because 29 - 23 = 6 = phi(9).

Maple

A192495 := proc(n) pn := numtheory[phi](n) ; for i from 1 do if ithprime(i+1) -ithprime(i) = pn then return ithprime(i) ; end if; end do: end proc:
seq(A192495(n), n=1..80) ; # R. J. Mathar, Jul 03 2011

Mathematica

a[n_] := If[n==1, 2, (For[m=1, Prime[m+1]-Prime[m]!= EulerPhi[n], m++ ]; Prime[m])]; Table[a[n], {n, 50}]

Crossrefs

Cf. A000010, A001223, A000230.

Sequence in context: A255254 A048848 A323256 * A162223 A133076 A295510

Adjacent sequences: A192492 A192493 A192494 * A192496 A192497 A192498

Keyword

nonn

Author

Michel Lagneau, Jul 02 2011

Extensions

Corrected by R. J. Mathar, Jul 03 2011

Status

approved