A126506 Number of base 11 n-digit numbers with adjacent digits differing by four or less.

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.

Links

Table of n, a(n) for n=0..19.

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

Adjacent sequences: A126503 A126504 A126505 * A126507 A126508 A126509

Keyword

nonn,base

Author

R. H. Hardin, Dec 28 2006

Status

approved