login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A125421 Number of base 9 circular n-digit numbers with adjacent digits differing by 7 or less. 0
1, 9, 79, 681, 5987, 52649, 463087, 4073225, 35827395, 315131721, 2771845519, 24380686185, 214448408099, 1886252068073, 16591155401263, 145933007686601, 1283602149301635, 11290348248219273, 99308001030865615 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

[Empirical] a(base,n)=a(base-1,n)+F(7) for base>=7.int(n/2)+1 and F(d) is the largest coefficient in (1+x+...+x^(2d))^n

LINKS

Table of n, a(n) for n=0..18.

FORMULA

Conjectures from Colin Barker, Jun 02 2017: (Start)

G.f.: (1 - x^2 - 14*x^3) / ((1 - x)*(1 - 8*x - 7*x^2)).

a(n) = 1 + (4-sqrt(23))^n + (4+sqrt(23))^n for n>0.

a(n) = 9*a(n-1) - a(n-2) - 7*a(n-3) for n>3.

(End)

PROG

(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-1](($[i]`-$[(i+1)mod N]`>7)+($[(i+1)mod N]`-$[i]`>7))

CROSSREFS

Sequence in context: A126632 A294344 A125909 * A163445 A190979 A254598

Adjacent sequences:  A125418 A125419 A125420 * A125422 A125423 A125424

KEYWORD

nonn,base

AUTHOR

R. H. Hardin, Dec 28 2006

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 22 02:46 EST 2022. Contains 350481 sequences. (Running on oeis4.)