A087030 -id:A087030 - cp's OEIS frontend

A087031 Numbers n such that 2p-n is prime, p is the smallest prime > n.

1, 3, 9, 15, 27, 31, 33, 39, 47, 57, 61, 63, 69, 75, 91, 93, 99, 105, 115, 117, 123, 135, 141, 147, 151, 159, 167, 177, 183, 185, 189, 195, 199, 213, 217, 219, 225, 237, 245, 251, 257, 267, 271, 273, 279, 297, 301, 303, 309, 325, 341, 345, 361, 367, 375

Offset: 1

Zak Seidov, Jul 31 2003

			3 is a term because smallest prime >3 is 5 and 2*5-3=7 is prime.

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

Cf. A087030.

Select[Range[400],PrimeQ[2*NextPrime[#]-#]&] (* Harvey P. Dale, Jul 02 2018 *)

isok(n) = isprime(2*nextprime(n+1) - n);  \\ Michel Marcus, Oct 03 2013

Corrected by Michel Marcus, Oct 03 2013

A087032 a(n) = 1 if 2*A151800(n) - n is prime, otherwise 0, where A151800(n) is the smallest prime > n.

Original entry on oeis.org

1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0

Offset: 1

Zak Seidov, Jul 31 2003

There is no subsequence of two ones; number of zeros in each group is odd, see A087033.

			a(1)=1 because the smallest prime > 1 is 2 and 2*2-1=3 is prime.

Antti Karttunen, Table of n, a(n) for n = 1..100000
Index entries for characteristic functions

Cf. A010051, A087030, A087033, A151800.

bb={}; Do[bb={bb, If[PrimeQ[2(Prime[PrimePi[n]+1])-n], 1, 0]}, {n, 1000}]; Flatten[bb]

A087032(n) = isprime((2*nextprime(1+n))-n); \\ Antti Karttunen, Oct 09 2018

a(n) = 1 if A087030(n) is prime, 0 if it is composite.

a(n) = A010051((2*A151800(n))-n). - Antti Karttunen, Oct 09 2018

Definition edited by Antti Karttunen, Oct 09 2018

cp's OEIS Frontend

A087031 Numbers n such that 2p-n is prime, p is the smallest prime > n.

Views

Author

Keywords

Examples

Links

Crossrefs

Programs

Mathematica

PARI

Extensions