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A126375 Number of base 21 n-digit numbers with adjacent digits differing by one or less. 4
1, 21, 61, 179, 527, 1555, 4595, 13593, 40245, 119235, 353459, 1048285, 3110249, 9231305, 27407185, 81392387, 241773327, 718335747, 2134675683, 6344739309, 18861068265, 56076828573, 166747755621, 495896780609, 1474935978225 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

[Empirical] a(base,n)=a(base-1,n)+3^(n-1) for base>=n; a(base,n)=a(base-1,n)+3^(n-1)-2 when base=n-1.

LINKS

Table of n, a(n) for n=0..24.

FORMULA

G.f.: (1+10*x-126*x^2+366*x^3-166*x^4-700*x^5+679*x^6+426*x^7-466*x^8-104*x^9+73*x^10+6*x^11) / ((1-x)*(1-10*x+34*x^2-32*x^3-54*x^4+100*x^5+23*x^6-76*x^7-10*x^8+12*x^9+x^10)) (conjectured). - Colin Barker, Jul 18 2017

PROG

(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>1)+($[i+1]`-$[i]`>1))

CROSSREFS

Sequence in context: A325319 A069133 A124714 * A146468 A081302 A058100

Adjacent sequences:  A126372 A126373 A126374 * A126376 A126377 A126378

KEYWORD

nonn,base

AUTHOR

R. H. Hardin, Dec 26 2006

STATUS

approved

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Last modified October 1 04:31 EDT 2022. Contains 357134 sequences. (Running on oeis4.)