A092913 - OEIS

A092913

a(0) = 1; a(n) = least multiple of a(n-1) such that every k with a(n)-n <= k <= a(n) + n is composite. The least distance of a prime on either side from a(n) is >n.

1, 9, 117, 117, 1404, 5616, 5616, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 190944, 3246048, 3246048, 38952576, 38952576, 38952576, 38952576, 38952576, 38952576

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..30.

EXAMPLE

a(2) = a(3) = 117 = 9*13 and all the numbers from 117-2 = 115 to 117+2 = 119 are

composite.

MATHEMATICA

f[s_] := Block[{k, n, inc}, n = Length[s]; k = inc = Last[s]; While[Or @@ PrimeQ /@ Range[k - n, k + n], k += inc]; Append[s, k]]; Nest[f, {1}, 30] (* Ray Chandler, Sep 23 2006 *)

CROSSREFS

Sequence in context: A083305 A222146 A253655 * A022607 A139740 A221442

Adjacent sequences: A092910 A092911 A092912 * A092914 A092915 A092916

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Mar 15 2004

EXTENSIONS

Extended by Ray Chandler, Sep 23 2006

STATUS

approved