OFFSET
0,2
COMMENTS
a(1),a(2),a(3),a(4),a(5) are (between the two 0's) the cores of the decimal expansions of a(10),a(11),a(12),a(13),a(14).
First differences begin 130,12300,1223000,122230000,....
LINKS
Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000).
FORMULA
a(n) = 2*A003555(n+1).
n 1's followed by n 8's is b(n)=18,1188,111888,11118888,1111188888, ...; then a(n)=b(n)/9. See its "contrary" A184337(n+1).
G.f.: 2*x*(-1+45*x) / ( (x-1)*(100*x-1)*(10*x-1) ). - R. J. Mathar, Mar 10 2011
EXAMPLE
a(1)=1*2=2, a(2)=11*12=132, a(3)=111*112=12432.
MATHEMATICA
LinearRecurrence[{111, -1110, 1000}, {0, 2, 132}, 20] (* Harvey P. Dale, Apr 08 2022 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, Feb 14 2011
EXTENSIONS
Zero added by Franklin T. Adams-Watters, Mar 09 2011
STATUS
approved