OFFSET
1,1
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
FORMULA
a(n) = pi(3n+3) - pi(3n), where pi(n) = A000720(n). - Ridouane Oudra, Sep 02 2019
MATHEMATICA
Boole[PrimeQ/@Flatten[Table[6n+{-1, 1}, {n, 60}]]] (* Harvey P. Dale, Jun 04 2017 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Stephan Wagler (stephanwagler(AT)aol.com), Oct 08 2002
EXTENSIONS
Offset corrected by N. J. A. Sloane, Feb 02 2009
STATUS
approved