A129227 a(n) is that prime number, p, less than n*Pi such that n*Pi/p has the smallest fractional part.

3, 3, 3, 11, 5, 17, 7, 5, 7, 31, 17, 37, 37, 43, 47, 5, 53, 53, 59, 31, 13, 23, 71, 73, 13, 79, 83, 29, 13, 47, 97, 97, 103, 53, 109, 113, 29, 17, 61, 31, 127, 131, 67, 137, 47, 71, 73, 149, 151, 157, 157, 163, 83, 167, 43, 173, 179, 181, 37, 47, 191, 97, 197, 67, 17, 103

Offset

1,1

Links

Table of n, a(n) for n=1..66.

Example

a(4)=11 because 4*Pi/11 = 1.142... and the fractional part 0.142... represents the smallest remainder resulting from the division of 4*Pi by a prime number less than 4*Pi.

Mathematica

f[n_] := (p = Denominator[ Min[ FractionalPart[(n*Pi / Prime@ Range@ PrimePi[n*Pi])]] [[2]]]; If[p == 1, n, p]); Array[f, 66] (* Robert G. Wilson v, Apr 08 2007 *)

Prog

(Sage) A129227 = lambda n: sorted(primes(floor(n*pi)+1), key=lambda p: (n*pi/p-floor(n*pi/p)))[0] # D. S. McNeil, Dec 11 2010

Crossrefs

Cf. A129228.

Sequence in context: A278822 A274487 A141794 * A252748 A346869 A097161

Adjacent sequences: A129224 A129225 A129226 * A129228 A129229 A129230

Keyword

easy,nonn

Author

Axel Harvey, Apr 04 2007

Extensions

Edited and extended by Robert G. Wilson v, Apr 08 2007

Status

approved