A075743 For all numbers of the form 6 +- 1 starting with 5,7,11,13,..., '1' indicates prime and '0' indicates composite.

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

Offset: 1

Author

Stephan Wagler (stephanwagler(AT)aol.com), Oct 08 2002

Keywords

• easy
• nonn

Comments

The sequence may described as: for all numbers k(n) [k(n) = 6*ceiling(n/2) + (-1)^n] congruent to -1 or +1 (mod 6) starting with k(n) = {5,7,11,13,...}, a(k(n)) is 1 if k(n) is prime and 0 if k(n) is composite. - Daniel Forgues, Mar 01 2009

Links

• Daniel Forgues, Table of n, a(n) for n = 1..33332

Crossrefs

Cf. A000040, A000720, A007310, A010051.

Absolute value of A156706.

Programs

Mathematica

Boole[PrimeQ/@Flatten[Table[6n+{-1,1},{n,60}]]] (* Harvey P. Dale, Jun 04 2017 *)

Formula

a(n) = A010051(A007310(n+2)). - Reinhard Zumkeller, Oct 02 2008

a(n) = pi(3n+3) - pi(3n), where pi(n) = A000720(n). - Ridouane Oudra, Sep 02 2019

Extensions

Offset corrected by N. J. A. Sloane, Feb 02 2009