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!)
A126489 Number of base 21 n-digit numbers with adjacent digits differing by three or less. 2
1, 21, 135, 889, 5903, 39389, 263647, 1768457, 11880131, 79895207, 537729241, 3621234957, 24396753479, 164414536077, 1108268954317, 7471720473245, 50378750794147, 339712511249557, 2290882896563443, 15449485988902675 (list; graph; refs; listen; history; text; internal format)
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.

LINKS

Table of n, a(n) for n=0..19.

FORMULA

G.f.: (1+9*x-84*x^2-2*x^3+321*x^4+70*x^5-178*x^6-26*x^7+13*x^8+2*x^9) / (1-12*x+33*x^2+36*x^3-125*x^4-55*x^5+70*x^6+16*x^7-5*x^8-x^9) (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 21 differing by two or less A126408, one or less A126375.

Sequence in context: A243201 A264554 A125331 * A033595 A220388 A220151

Adjacent sequences: A126486 A126487 A126488 * A126490 A126491 A126492

KEYWORD

nonn,base

AUTHOR

R. H. Hardin, Dec 27 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 20 22:57 EDT 2023. Contains 361392 sequences. (Running on oeis4.)