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A126481
Number of base 13 n-digit numbers with adjacent digits differing by three or less.
2
1, 13, 79, 497, 3159, 20181, 129205, 828005, 5308457, 34039495, 218289367, 1399900567, 8977768487, 57576133509, 369247743009, 2368065719909, 15186926536617, 97397125090807, 624629410666375, 4005887424197615
OFFSET
0,2
COMMENTS
[Empirical] a(base,n)=a(base-1,n)+7^(n-1) for base>=3n-2; a(base,n)=a(base-1,n)+7^(n-1)-2 when base=3n-3.
FORMULA
G.f.: (1+5*x-19*x^2-29*x^3+16*x^4+20*x^5-2*x^6-2*x^7) / (1-8*x+6*x^2+28*x^3-5*x^4-18*x^5+2*x^7) (conjectured). - Colin Barker, Jul 18 2017
PROG
(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>3)+($[i+1]`-$[i]`>3))
CROSSREFS
Cf. Base 13 differing by two or less A126400, one or less A126367.
Sequence in context: A081584 A125323 A075584 * A032625 A120782 A032652
KEYWORD
nonn,base
AUTHOR
R. H. Hardin, Dec 27 2006
STATUS
approved