A022459 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A022459

a(n) = prime(2n+1) mod prime(n).

1, 2, 2, 2, 9, 2, 13, 2, 21, 15, 21, 23, 21, 23, 33, 31, 31, 35, 33, 37, 45, 39, 45, 49, 39, 39, 51, 55, 59, 57, 53, 51, 57, 69, 55, 65, 65, 63, 67, 73, 73, 77, 67, 75, 73, 89, 77, 63, 69, 89, 97, 93, 105, 97, 93, 91, 93, 101, 99, 99, 111, 105, 95, 105, 113, 117

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

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

FORMULA

a(n) = A031368(n+1) modulo A000040(n). - Michel Marcus, Sep 30 2013

For n > 8, a(n) = prime(2n+1) - 2*prime(n). - Charles R Greathouse IV, Sep 30 2013

MATHEMATICA

Table[Mod[Prime[2*n + 1], Prime[n]], {n, 100}] (* T. D. Noe, Sep 30 2013 *)

PROG

(PARI) a(n) = prime(2*n+1) % prime(n); \\ Michel Marcus, Sep 30 2013

(PARI) v=vector(100, i, 1); p=2; q=5; for(n=2, #v, q=nextprime(nextprime(q+1) + 1); p=nextprime(p+1); v[n]=q%p); v \\ Charles R Greathouse IV, Sep 30 2013

(Magma) [NthPrime(2*n+1) mod NthPrime(n): n in [1..50]]; // G. C. Greubel, Feb 28 2018

CROSSREFS

Sequence in context: A075097 A138056 A340080 * A060804 A086364 A260662

Adjacent sequences: A022456 A022457 A022458 * A022460 A022461 A022462

KEYWORD

nonn

AUTHOR

Clark Kimberling

EXTENSIONS

Missing term a(57) inserted by Michel Marcus, Sep 30 2013

STATUS

approved