

A079953


Smallest prime p such that prime(n) mod 2*p = prime(n).


4



2, 2, 3, 5, 7, 7, 11, 11, 13, 17, 17, 19, 23, 23, 29, 29, 31, 31, 37, 37, 37, 41, 43, 47, 53, 53, 53, 59, 59, 59, 67, 67, 71, 71, 79, 79, 79, 83, 89, 89, 97, 97, 97, 97, 101, 101, 107, 113, 127, 127, 127, 127, 127, 127, 131, 137, 137, 137, 139, 149, 149, 149, 157, 157
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OFFSET

1,1


COMMENTS

a(n) is smallest prime greater than prime(n)/2.  Peter Munn, Sep 18 2017


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000


FORMULA

T(n, A049084(a(n))) = A000040(n), T defined as in A079950.
a(n) = nextprime(prime(n)/2) ~ (n log n)/2.  Charles R Greathouse IV, Mar 17 2015


EXAMPLE

n=6: prime(6)=13 and 13 mod(2*2)=1, 13 mod(2*3)=1, 13 mod(2*5)=3, 13 mod(2*7)=13, therefore a(6)=7.


MATHEMATICA

f[n_] := Block[{p = 2}, While[Prime@ n != Mod[Prime@ n, 2 p], p = NextPrime@ p]; p]; Array[f, 64] (* Michael De Vlieger, Mar 17 2015 *)


PROG

(PARI) a(n, q=prime(n))=nextprime(q/2) \\ Charles R Greathouse IV, Mar 17 2015


CROSSREFS

Cf. A079952, A039734.
Sequence in context: A100142 A245935 A178880 * A133393 A126881 A290273
Adjacent sequences: A079950 A079951 A079952 * A079954 A079955 A079956


KEYWORD

nonn,easy


AUTHOR

Reinhard Zumkeller, Jan 19 2003


STATUS

approved



