login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A192495 Smallest prime p such that there is a gap of phi(n) between p and next prime. 1
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 16 09:13 EDT 2020. Contains 335784 sequences. (Running on oeis4.)