OFFSET
0,3
COMMENTS
Each cell has 26 neighbors.
LINKS
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS
Index entries for linear recurrences with constant coefficients, signature (1,3,-3,-3,3,1,-1).
FORMULA
a(2n) = 46n^3 - 57n^2 + 57n - 19 for n>=1, a(2n+1) = 46n^3 - 51n^2 + 57n - 17 for n>=1. [Nathaniel Johnston, Nov 06 2010]
G.f.: x*(18*x^3+x^2+26*x+1)*(x^4+4*x^2+1) / ((x-1)^4*(x+1)^3). - Colin Barker, Feb 28 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Omar E. Pol, May 11 2009
EXTENSIONS
Edited by Omar E. Pol, Sep 05 2009
a(6) - a(27) from Nathaniel Johnston, Nov 06 2010
a(28) - a(38) from Colin Barker, Feb 28 2013
STATUS
approved