A179278 Largest nonprime integer not less than n.

1, 1, 1, 4, 4, 6, 6, 8, 9, 10, 10, 12, 12, 14, 15, 16, 16, 18, 18, 20, 21, 22, 22, 24, 25, 26, 27, 28, 28, 30, 30, 32, 33, 34, 35, 36, 36, 38, 39, 40, 40, 42, 42, 44, 45, 46, 46, 48, 49, 50, 51, 52, 52, 54, 55, 56, 57, 58, 58, 60, 60, 62, 63, 64, 65, 66, 66, 68, 69, 70, 70, 72

Offset

1,4

Links

Table of n, a(n) for n=1..72.

Formula

For n > 3: a(n) = A113523(n) = A014684(n);

For n > 0: a(n) = A113638(n). - Georg Fischer, Oct 12 2018

A005171(a(n)) = 1; A010051(a(n)) = 0.

Mathematica

Array[# - Boole[PrimeQ@ #] - Boole[# == 3] &, 72] (* Michael De Vlieger, Oct 13 2018 *)

Prog

(PARI) a(n) = if (isprime(n), if (n==3, 1, n-1), n); \\ Michel Marcus, Oct 13 2018

Crossrefs

Cf. A007917, A014684, A018252, A113523, A113638.

Sequence in context: A276679 A163638 A113523 * A365216 A132882 A171384

Adjacent sequences: A179275 A179276 A179277 * A179279 A179280 A179281

Keyword

nonn,easy

Author

Reinhard Zumkeller, Jul 08 2010

Status

approved