A126516 Number of base 21 n-digit numbers with adjacent digits differing by four or less.

1, 21, 169, 1401, 11729, 98733, 833745, 7053777, 59744071, 506355371, 4293250829, 36409762185, 308822547173, 2619602438143, 22221971988277, 188513351680519, 1599222568187231, 13566880665362081, 115094253790715069

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 21 differing by three or less A126489, two or less A126408, one or less A126375.

Sequence in context: A358930 A041848 A125358 * A241219 A185128 A007261

Adjacent sequences: A126513 A126514 A126515 * A126517 A126518 A126519

Keyword

nonn,base

Author

R. H. Hardin, Dec 28 2006

Status

approved