A126405 Number of base 18 n-digit numbers with adjacent digits differing by two or less.

1, 18, 84, 400, 1918, 9236, 44598, 215774, 1045480, 5071280, 24620610, 119613534, 581435182, 2827574694, 13755641338, 66937791112, 325807794512, 1586104016732, 7722649252978, 37605625036546, 183139080847344

Offset

0,2

Comments

[Empirical] a(base,n)=a(base-1,n)+5^(n-1) for base>=2n-1; a(base,n)=a(base-1,n)+5^(n-1)-2 when base=2n-2.

Links

Table of n, a(n) for n=0..20.

Formula

G.f.: (1+8*x-70*x^2+39*x^3+220*x^4-61*x^5-172*x^6+22*x^7+36*x^8) / (1-10*x+26*x^2+11*x^3-80*x^4-x^5+60*x^6-2*x^7-12*x^8) (conjectured). - Colin Barker, Jul 18 2017

Prog

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

Crossrefs

Cf. Base 18 differing by one or less A126372.

Sequence in context: A067984 A281372 A124935 * A250101 A141842 A215191

Adjacent sequences: A126402 A126403 A126404 * A126406 A126407 A126408

Keyword

nonn,base

Author

R. H. Hardin, Dec 28 2006

Status

approved