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A126506
Number of base 11 n-digit numbers with adjacent digits differing by four or less.
1
1, 11, 79, 591, 4441, 33391, 251077, 1887941, 14196143, 106746189, 802665137, 6035544031, 45383547985, 341256134861, 2566034493807, 19294987989285, 145086343307233, 1090959321972847, 8203337509713921, 61684010524412861
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.
FORMULA
G.f.: (1-x-x^2)*(1+4*x-2*x^2-4*x^3+2*x^4) / ((1-x)*(1-7*x-5*x^2+8*x^3+2*x^4-2*x^5)) (conjectured). - Colin Barker, Jul 17 2017
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 11 differing by three or less A126479, two or less A126398, one or less A126365.
Sequence in context: A125348 A337929 A155619 * A159663 A227244 A026897
KEYWORD
nonn,base
AUTHOR
R. H. Hardin, Dec 28 2006
STATUS
approved