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A126408
Number of base 21 n-digit numbers with adjacent digits differing by two or less.
3
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
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
KEYWORD
nonn,base
AUTHOR
R. H. Hardin, Dec 28 2006
STATUS
approved