OFFSET
0,2
COMMENTS
The number of heptagons in the n-th ring of the Klein Quartic. - Amiram Eldar, Nov 14 2023
REFERENCES
Arthur T. Benjamin and Jennifer J. Quinn, Proofs that really count: the art of combinatorial proof, M.A.A., 2003, p. 15.
LINKS
Tanya Khovanova, Recursive Sequences.
William P. Thurston, The Eightfold Way: A Mathematical Sculpture by Helaman Ferguson, in: The Eightfold Way: The Beauty of the Klein Quartic (ed. Silvio Levy), Cambridge University Press, New York, 1999, pp. 1-7.
Eric Weisstein's World of Mathematics, Klein Quartic.
Index entries for linear recurrences with constant coefficients, signature (1,1).
FORMULA
a(n) = round( ((14*phi-7)/5) * phi^n) (works for n>3). - Thomas Baruchel, Sep 08 2004
a(n) = 7*F(n) = F(n+4) + F(n-4) for n>3.
a(n) = A119457(n+5,n-1) for n>1. - Reinhard Zumkeller, May 20 2006
G.f.: 7*x/(1-x-x^2). - Philippe Deléham, Nov 20 2008
MATHEMATICA
a={}; b=0; c=7; AppendTo[a, b]; AppendTo[a, c]; Do[b=b+c; AppendTo[a, b]; c=b+c; AppendTo[a, c], {n, 1, 40, 1}]; a (* Vladimir Joseph Stephan Orlovsky, Jul 23 2008 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved