|
|
A126504
|
|
Number of base 9 n-digit numbers with adjacent digits differing by four or less.
|
|
2
|
|
|
1, 9, 61, 429, 3011, 21141, 148433, 1042167, 7317185, 51374875, 360709449, 2532586341, 17781606753, 124846894103, 876565722303, 6154478019155, 43211363078111, 303392406838867, 2130156189729353, 14956094122197975
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
COMMENTS
|
[Empirical] a(base,n)=a(base-1,n)+9^(n-1) for base>=4n-3; a(base,n)=a(base-1,n)+9^(n-1)-2 when base=4n-4.
|
|
LINKS
|
|
|
FORMULA
|
G.f.: (1 - x)*(1 + 3*x - x^3) / (1 - 7*x - x^2 + 6*x^3 - x^5).
a(n) = 7*a(n-1) + a(n-2) - 6*a(n-3) + a(n-5) for n>5.
(End)
|
|
PROG
|
(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>4)+($[i+1]`-$[i]`>4))
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|