A126508 Number of base 13 n-digit numbers with adjacent digits differing by four or less.

1, 13, 97, 753, 5897, 46287, 363509, 2855151, 22426249, 176152007, 1383628073, 10868042671, 85365689641, 670525630751, 5266807148873, 41369421713583, 324946216030489, 2552369333410047, 20048207650685929, 157473538310505327

Offset

0,2

Comments

[Empirical] a(base,n)=a(base-1,n)+9^(n-1) for base>=4n-3; a(base,n)=a(base-1,n)+9^(n-1)-2 when base=4n-4.

Links

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

Formula

G.f.: (1+4*x-14*x^2-16*x^3+22*x^4+8*x^5-8*x^6) / (1-9*x+6*x^2+26*x^3-18*x^4-12*x^5+8*x^6) (conjectured). - Colin Barker, Jul 18 2017

Prog

(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>4)+($[i+1]`-$[i]`>4))

Crossrefs

Cf. Base 13 differing by three or less A126481, two or less A126400, one or less A126367.

Sequence in context: A125350 A049294 A198480 * A228680 A372770 A158795

Adjacent sequences: A126505 A126506 A126507 * A126509 A126510 A126511

Keyword

nonn,base

Author

R. H. Hardin, Dec 28 2006

Status

approved