A126407 Number of base 20 n-digit numbers with adjacent digits differing by two or less.

1, 20, 94, 450, 2168, 10486, 50848, 247024, 1201730, 5852530, 28526860, 139144760, 679090456, 3315836420, 16196773236, 79141717426, 386812618952, 1891013450430, 9246370600422, 45218609940844, 221167392509842

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.

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 20 differing by one or less A126374.

Sequence in context: A071092 A144359 A124948 * A158446 A221704 A222772

Adjacent sequences: A126404 A126405 A126406 * A126408 A126409 A126410

Keyword

nonn,base

Author

R. H. Hardin, Dec 28 2006

Status

approved