OFFSET
1,7
COMMENTS
The matching rule is such that any elementary top-down triangle of three neighboring cells in the arrangement contains either one or three white cells.
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..500
A. Barbé, Symmetric patterns in the cellular automaton that generates Pascal's triangle modulo 2, Discr. Appl. Math. 105(2000), 1-38.
FORMULA
a(n) = 2^(floor(n/3) + (n mod 3) mod 2 - 1) - 2^(floor((n+3)/6) + d(n)-1), with d(n)=1 if n mod 6=1, otherwise d(n)=0.
Empirical g.f.: x^4*(x^2 - x + 1)*(x^2 + x + 1) / ((2*x^3-1)*(2*x^6-1)). - Colin Barker, Aug 29 2013
PROG
(PARI) { for (n=1, 500, write("b060550.txt", n, " ", 2^(floor(n/3) + (n%3)%2 - 1) - 2^(floor((n + 3)/6) + (n%6==1) - 1)); ) } \\ Harry J. Smith, Jul 07 2009
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
André Barbé (Andre.Barbe(AT)esat.kuleuven.ac.be), Apr 03 2001
STATUS
approved