OFFSET
1,1
COMMENTS
Number of words of length n using a 10 symbol alphabet where neighboring letters are neighbors in the alphabet. - Andrew Howroyd, Apr 17 2017
LINKS
Joseph Myers, BMO 2008--2009 Round 1 Problem 1---Generalisation
Index entries for linear recurrences with constant coefficients, signature (1, 4, -3, -3, 1).
FORMULA
G.f.: 2*x*(5+4*x-12*x^2-6*x^3+3*x^4)/(1-x-4*x^2+3*x^3+3*x^4-x^5) [From Maksym Voznyy (voznyy(AT)mail.ru), Aug 11 2009]
MATHEMATICA
LinearRecurrence[{1, 4, -3, -3, 1}, {10, 18, 34, 64, 122}, 31] (* Jean-François Alcover, Jul 01 2018 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Joseph Myers, Dec 24 2008
EXTENSIONS
G.f. proposed by Maksym Voznyy checked and corrected by R. J. Mathar, Sep 16 2009.
STATUS
approved