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A126539
Number of base 18 n-digit numbers with adjacent digits differing by five or less.
0
1, 18, 168, 1628, 15938, 156652, 1541646, 15178334, 149460562, 1471805948, 14493780280, 142729983350, 1405560587628, 13841533266014, 136307239633698, 1342312628779666, 13218690669418640, 130173687322873468
OFFSET
0,2
COMMENTS
[Empirical] a(base,n)=a(base-1,n)+11^(n-1) for base>=5n-4; a(base,n)=a(base-1,n)+11^(n-1)-2 when base=5n-5.
FORMULA
G.f.: (1+6*x-33*x^2-51*x^3+76*x^4+64*x^5-36*x^6-20*x^7) / (1-12*x+15*x^2+67*x^3-52*x^4-72*x^5+28*x^6+20*x^7) (conjectured). - Colin Barker, Jul 18 2017
PROG
(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>5)+($[i+1]`-$[i]`>5))
CROSSREFS
Cf. Base 18 differing by four or less A126513, three or less A126486, two or less A126405, one or less A126372.
Sequence in context: A327792 A071539 A125381 * A213802 A161499 A162346
KEYWORD
nonn,base
AUTHOR
R. H. Hardin, Dec 28 2006
STATUS
approved