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

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

1,1

Comments

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

Links

Antti Karttunen, Table of n, a(n) for n = 1..100000

Index entries for characteristic functions

Formula

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

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A010051, A087030, A087033, A151800.

Sequence in context: A016334 A154271 A225569 * A236677 A190236 A190224

Adjacent sequences: A087029 A087030 A087031 * A087033 A087034 A087035

Keyword

easy,nonn

Author

Zak Seidov, Jul 31 2003

Extensions

Definition edited by Antti Karttunen, Oct 09 2018

Status

approved