A287827 Number of sequences over the alphabet {0,1,...,9} such that no two consecutive terms have distance 3.
1, 10, 86, 742, 6404, 55274, 477082, 4117804, 35541714, 306768722, 2647791524, 22853698754, 197255539962, 1702558017644, 14695170558994, 126837403201602, 1094762853302164, 9449150445514434, 81557794797885642, 703944119701429084, 6075903902137709074
Offset: 0
Links
- Index entries for linear recurrences with constant coefficients, signature (9, -1, -20, 10).
Crossrefs
Programs
-
Mathematica
LinearRecurrence[{9, -1, -20, 10}, {1, 10, 86, 742, 6404}, 30]
-
Python
def a(n): if n in [0, 1, 2, 3, 4]: return [1, 10, 86, 742, 6404][n] return 9*a(n-1)-a(n-2)-20*a(n-3)+10*a(n-4)
Formula
For n>4, a(n) = 9*a(n-1) - a(n-2) - 20*a(n-3) + 10*a(n-4), a(0)=1, a(1)=10, a(2)=86, a(3)=742, a(4)=6404.
G.f.: (-1 - x + 3*x^2 + 2*x^3 - 2*x^4)/(-1 + 9*x - x^2 - 20*x^3 + 10*x^4).
Comments