OFFSET
0,2
REFERENCES
Edward J. Barbeau, Murray S. Klamkin & William O. J. Moser, Five Hundred Mathematical Challenges, Problem 284 at pp. 142-143 (1995).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (20, -100).
FORMULA
a(n) = 45*n*10^(n-1).
a(n) = 20*a(n-1) - 100*a(n-2), a(0)=0, a(1)=45. - Harvey P. Dale, Oct 09 2011
G.f.: (45*x)/(10*x-1)^2. - Harvey P. Dale, Oct 09 2011
a(n) = (9*n*10^n)/2. - Harvey P. Dale, Apr 23 2018
MAPLE
seq(45*n*10^(n-1), n=0..30); # Robert Israel, Jun 29 2018
MATHEMATICA
Table[45n 10^(n-1), {n, 0, 20}] (* or *) LinearRecurrence[{20, -100}, {0, 45}, 21] (* Harvey P. Dale, Oct 09 2011 *)
PROG
(PARI) a(n)=45*n*10^(n-1) \\ Charles R Greathouse IV, Oct 07 2015
(Magma) [45*n*10^(n-1): n in [0..30]]; // Vincenzo Librandi, Jun 30 2018
CROSSREFS
KEYWORD
nonn,easy,base
AUTHOR
EXTENSIONS
More terms from James A. Sellers, Jan 19 2000
STATUS
approved