A131695 a(n) = 0 iff 2*prime(n+1) = prime(n) + prime(n+2), otherwise a(n) = 1.

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

Offset: 1

Author

Giovanni Teofilatto, Sep 15 2007

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000
• Index entries for characteristic functions

Crossrefs

Cf. A001223, A122535, A064113 (positions of zeros).

Programs

Mathematica

Table[Boole[2 Prime[n + 1] != Prime@ n + Prime[n + 2]], {n, 120}] (* Michael De Vlieger, Dec 17 2016 *)

PARI

A131695(n) = ((2*prime(1+n)) != (prime(n)+prime(2+n))); \\ Antti Karttunen, Aug 30 2017

Formula

a(n) = A098726(n) - 2. - Filip Zaludek, Dec 16 2016

Extensions

Definition and values corrected, keyword:cons removed; R. J. Mathar, Apr 22 2010