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A126483
Number of base 15 n-digit numbers with adjacent digits differing by three or less.
2
1, 15, 93, 595, 3845, 24983, 162805, 1062635, 6941843, 45369865, 296598577, 1939229883, 12680054343, 82914396455, 542185539797, 3545445779213, 23184429833549, 151608454599649, 991405196934357, 6483050068051005
OFFSET
0,2
COMMENTS
[Empirical] a(base,n)=a(base-1,n)+7^(n-1) for base>=3n-2; a(base,n)=a(base-1,n)+7^(n-1)-2 when base=3n-3.
FORMULA
G.f.: (1+6*x-31*x^2-40*x^3+48*x^4+35*x^5-19*x^6-5*x^7+2*x^8) / (1-9*x+11*x^2+37*x^3-20*x^4-29*x^5+8*x^6+4*x^7-x^8) (conjectured). - Colin Barker, Jul 18 2017
PROG
(S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-2](($[i]`-$[i+1]`>3)+($[i+1]`-$[i]`>3))
CROSSREFS
Cf. Base 15 differing by two or less A126402, one or less A126369.
Sequence in context: A052226 A108684 A125325 * A226766 A114240 A189657
KEYWORD
nonn,base
AUTHOR
R. H. Hardin, Dec 27 2006
STATUS
approved