A007920 Smallest number k such that n + k is prime.

2, 1, 0, 0, 1, 0, 1, 0, 3, 2, 1, 0, 1, 0, 3, 2, 1, 0, 1, 0, 3, 2, 1, 0, 5, 4, 3, 2, 1, 0, 1, 0, 5, 4, 3, 2, 1, 0, 3, 2, 1, 0, 1, 0, 3, 2, 1, 0, 5, 4, 3, 2, 1, 0, 5, 4, 3, 2, 1, 0, 1, 0, 5, 4, 3, 2, 1, 0, 3, 2, 1, 0, 1, 0, 5, 4, 3, 2, 1, 0, 3, 2, 1, 0, 5, 4, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 3, 2, 1, 0, 1, 0, 3, 2, 1, 0, 1

Offset

0,1

Comments

a(n) = A007918(n) - n.

Links

T. D. Noe, Table of n, a(n) for n = 0..10000

M. Popescu, V. Seleacu, About the Smarandache Complementary Prime Function, Smarandache Notions Journal, Vol. 7, No. 1-2-3, 1996, 12-22.

F. Smarandache, Only Problems, Not Solutions!, via viXra.

Example

a(22) = 1 because 22 + 1 = 23, the next higher prime.
a(23) = 0 because 23 is prime.
a(24) = 5 because 24 + 5 = 29, the next higher prime.
a(25) = 4 because 25 + 4 = 29, the next higher prime.

Mathematica

distToPrime[n_] := If[PrimeQ[n], 0, NextPrime[n] - n]; Array[distToPrime, 110, 0] (* Harvey P. Dale, Sep 19 2011 *)

Prog

(PARI) a(n)=nextprime(n)-n

Crossrefs

Cf. A064722, A013632 (a slightly different version).

Sequence in context: A246398 A051699 A328682 * A127587 A175832 A330961

Adjacent sequences: A007917 A007918 A007919 * A007921 A007922 A007923

Keyword

nonn,easy

Author

R. Muller

Extensions

More terms from Joanna S. Bartlett (s1117611(AT)cedarville.edu)

Status

approved