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URL: https://oeis.org/A126396

⇱ A126396 - OEIS

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A126396
Number of base 9 n-digit numbers with adjacent digits differing by two or less.
3
1, 9, 39, 175, 793, 3611, 16475, 75229, 343633, 1569883, 7172423, 32769925, 149723361, 684077955, 3125520983, 14280373781, 65246447425, 298108406323, 1362045450407, 6223131628517, 28433241805745, 129910355608771
OFFSET
0,2
COMMENTS
[Empirical] a(base,n)=a(base-1,n)+5^(n-1) for base>=2n-1; a(base,n)=a(base-1,n)+5^(n-1)-2 when base=2n-2.
FORMULA
Conjectures from Colin Barker, Jun 01 2017: (Start)
G.f.: (1 + 3*x - 10*x^2 - 6*x^3 + 6*x^4 + 2*x^5) / (1 - 6*x + 5*x^2 + 8*x^3 - 4*x^4 - 2*x^5).
a(n) = 6*a(n-1) - 5*a(n-2) - 8*a(n-3) + 4*a(n-4) + 2*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]`-$[i+1]`>2)+($[i+1]`-$[i]`>2))
CROSSREFS
Cf. Base 9 differing by one or less A126363.
Sequence in context: A317019 A124041 A264085 * A246065 A075210 A146187
KEYWORD
nonn,base
AUTHOR
R. H. Hardin, Dec 28 2006
STATUS
approved