OFFSET
1,2
COMMENTS
a(n) must be chosen with nonzero rightmost digit.
FORMULA
For n == 0 (mod 3), a(n) = 10^(n/3) + 2; for n == 1 (mod 3), n>1, a(n) = 2*10^((n-1)/3) + 1; for n == 2 (mod 3), a(n) = 10^((n+1)/3) + 1. - Sam Alexander, Jan 04 2005
From Chai Wah Wu, Jun 02 2016: (Start)
a(n) = 11*a(n-3) - 10*a(n-6) for n > 7.
G.f.: x*(1 + x + 2*x^2)*(1 + 10*x - 10*x^3 - 10*x^4)/((1 - x)*(1 - 10*x^3)*(1 + x + x^2)). (End)
a(n) = (1-sign((n-1) mod 3))*10^floor(n/3)+10^floor((n+1)/3)-sign(n mod 3)+2, for n > 1. - Wesley Ivan Hurt, Mar 06 2022
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Eric Angelini, Oct 01 2004
EXTENSIONS
More terms from Sam Alexander, Jan 04 2005
More terms from David Wasserman, Feb 26 2008
STATUS
approved