A126515 Number of base 20 n-digit numbers with adjacent digits differing by four or less.

1, 20, 160, 1320, 11000, 92172, 774696, 6522504, 54969166, 463511924, 3909629218, 32982588380, 278275931230, 2347955939840, 19811499262410, 167167589771462, 1410557938634156, 11902332555068524, 100432557218234836

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..18.

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 20 differing by three or less A126488, two or less A126407, one or less A126374.

Sequence in context: A159470 A059601 A125357 * A118676 A067534 A041768

Adjacent sequences: A126512 A126513 A126514 * A126516 A126517 A126518

Keyword

nonn,base

Author

R. H. Hardin, Dec 28 2006

Status

approved