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A126475 Number of base 7 n-digit numbers with adjacent digits differing by three or less. 3
1, 7, 37, 203, 1111, 6083, 33305, 182349, 998383, 5466269, 29928491, 163862147, 897165287, 4912089625, 26894291201, 147249532159, 806209189861, 4414093873755, 24167703582839, 132321131623579, 724474371929041 (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..20.

FORMULA

Conjectures from Colin Barker, Jun 01 2017: (Start)

G.f.: (1 + 2*x - x^2 - x^3) / (1 - 5*x - 3*x^2 + 2*x^3 + x^4).

a(n) = 5*a(n-1) + 3*a(n-2) - 2*a(n-3) - a(n-4) for n>3.

(End)

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 7 differing by two or less A126394, one or less A126361.

Sequence in context: A002807 A124610 A002683 * A274674 A255672 A077239

Adjacent sequences:  A126472 A126473 A126474 * A126476 A126477 A126478

KEYWORD

nonn,base

AUTHOR

R. H. Hardin, Dec 27 2006

STATUS

approved

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Last modified August 16 16:12 EDT 2018. Contains 313809 sequences. (Running on oeis4.)