A113523 a(n) = largest composite nonnegative integer <= n.

0, 0, 0, 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

Comments

For n > 3: a(n) = A179278(n). - Reinhard Zumkeller, Jul 08 2010

Links

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

Formula

a(1) = a(2) = a(3) = 0. For n >= 4, a(n) = A014684(n).

Mathematica

nnci[n_]:=Module[{k=0}, While[PrimeQ[n-k], k++]; n-k]/.{1->0}; Array[nnci, 80] (* Harvey P. Dale, Jul 19 2012 *)

Prog

(PARI) a(n) = if(n<4, 0, n-isprime(n)); \\ Bruce Nye, Jun 16 2026

Crossrefs

Cf. A007917, A014684.

Sequence in context: A175123 A276679 A163638 * A179278 A365216 A132882

Adjacent sequences: A113520 A113521 A113522 * A113524 A113525 A113526

Keyword

nonn,changed

Author

Leroy Quet, Jan 12 2006

Status

approved