OFFSET
1,3
COMMENTS
The length of the n-th term is floor((n+1)/3) digits, for all n>1. [Corrected by M. F. Hasler, Jun 23 2017]
LINKS
Index entries for linear recurrences with constant coefficients, signature (0, 0, 11, 0, 0, -10).
FORMULA
a(3n) = floor(10^n/3) (= n times the digit '3'), a(3n+1) = floor(10^n/3)*2 (= n times the digit '6'), a(3n+2) = floor(10^(n+1)/6) - floor(10^n/9) (= digit '1' followed by n digits '5'). - M. F. Hasler, Jun 23 2017
G.f.: x^2*(1+x)*(4*x^2+2*x+1) / ( (x-1)*(1+x+x^2)*(10*x^3-1) ). - R. J. Mathar, Jun 29 2017
PROG
(PARI) { my(x='x+O('x^33)); concat([0], Vec( x*(1+x)*(1+2*x+4*x^2)/((1-x)*(1+x+x^2)*(1-10*x^3)) )) } \\ Joerg Arndt, Jun 21 2017
(PARI) A289006(n)=if(n%3==2, 10^(n\3+1)\6-10^(n\3)\9, 10^(n\3)\3<<(n%3)) \\ M. F. Hasler, Jun 23 2017
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Peter Schonefeld, Jun 21 2017
STATUS
approved