

A051697


Closest prime to n (break ties by taking the smaller prime).


22



2, 2, 2, 3, 3, 5, 5, 7, 7, 7, 11, 11, 11, 13, 13, 13, 17, 17, 17, 19, 19, 19, 23, 23, 23, 23, 23, 29, 29, 29, 29, 31, 31, 31, 31, 37, 37, 37, 37, 37, 41, 41, 41, 43, 43, 43, 47, 47, 47, 47, 47, 53, 53, 53, 53, 53, 53, 59, 59, 59, 59, 61, 61, 61, 61, 67, 67, 67, 67, 67, 71, 71
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OFFSET

0,1


LINKS

Table of n, a(n) for n=0..71.
Eric Weisstein's World of Mathematics, Nearest Prime


EXAMPLE

Closest primes to 0,1,2,3,4 are 2,2,2,3,3.


MATHEMATICA

a[n_] := (np = NextPrime[n]; pp = Prime[PrimePi[np]  1]; Which[np > 2npp, pp, np < 2npp, np, True, pp]); a[0] = a[1] = 2; Table[a[n], {n, 0, 71}] (* JeanFrançois Alcover, Jul 28 2011 *)


PROG

(PARI) a(n)=if(n<3, return(2)); my(p=precprime(n), q=nextprime(n)); if(qn<np, q, p) \\ Charles R Greathouse IV, Apr 28 2015


CROSSREFS

Related sequences: A023186A023188, A046929A046931, A051650, A051652, A051697A051702, A051728A051730.
Sequence in context: A224908 A029097 A210955 * A240869 A065308 A035680
Adjacent sequences: A051694 A051695 A051696 * A051698 A051699 A051700


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms from James A. Sellers


STATUS

approved



