OFFSET
2,1
LINKS
R. H. Hardin, Table of n, a(n) for n=2..100
Index entries for linear recurrences with constant coefficients, signature (20,-100).
FORMULA
a(n) = (copies*n)*(copies+1)^(n-2).
From G. C. Greubel, Jun 01 2018: (Start)
a(n) = 9*n*10^(n-2).
G.f.: x^2*(18-90*x)/(1-20*x+100*x^2).
E.g.f.: 9*x*exp(10*x)/10. (End)
From Amiram Eldar, May 16 2022: (Start)
Sum_{n>=2} 1/a(n) = (100/9)*log(10/9) - 10/9.
Sum_{n>=2} (-1)^n/a(n) = 10/9 - (100/9)*log(11/10). (End)
MATHEMATICA
LinearRecurrence[{20, -100}, {18, 270}, 30] (* or *) Table[9*n*10^(n-2), {n, 2, 30}] (* G. C. Greubel, Jun 01 2018 *)
PROG
(PARI) m=30; v=concat([18, 270], vector(m-2)); for(n=3, m, v[n]=20*v[n-1] -100*v[n-2]); v \\ G. C. Greubel, Jun 01 2018
(Magma) I:=[18, 270]; [n le 2 select I[n] else 20*Self(n-1) - 100*Self(n-2): n in [1..10]]; // G. C. Greubel, Jun 01 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 20 2009
STATUS
approved