A126408 Number of base 21 n-digit numbers with adjacent digits differing by two or less.

1, 21, 99, 475, 2293, 11111, 53973, 262649, 1279855, 6243155, 30479985, 148910385, 727918557, 3559976043, 17417455619, 85244931269, 417326666085, 2043565752795, 10008988327829, 49030629716903, 240219997723397

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 21 differing by one or less A126375.

Sequence in context: A140370 A124949 A267681 * A157329 A356738 A044272

Adjacent sequences: A126405 A126406 A126407 * A126409 A126410 A126411

Keyword

nonn,base

Author

R. H. Hardin, Dec 28 2006

Status

approved