OFFSET
0,2
COMMENTS
Sum of n-th row of triangle of powers of 9: 1; 1 9 1; 1 9 81 9 1; 1 9 81 729 81 9 1; ... - Philippe Deléham, Feb 22 2014
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..500
Index entries for linear recurrences with constant coefficients, signature (10,-9).
FORMULA
G.f.: (1+x)/((1-x)*(1-9x)).
a(n) = (5/4)*9^n - 1/4.
Bisection of A135522/3. a(n+1)=9*a(n)+2. - Paul Curtz, Apr 22 2008
a(n) = Sum_{k=0..n} A112468(n,k)*10^k. - Philippe Deléham, Feb 22 2014
EXAMPLE
a(0) = 1;
a(1) = 1 + 9 + 1 = 11;
a(2) = 1 + 9 + 81 + 9 + 1 = 101;
a(3) = 1 + 9 + 81 + 729 + 81 + 9 + 1 = 911; etc. - Philippe Deléham, Feb 22 2014
MATHEMATICA
Table[(5*9^n - 1)/4, {n, 0, 18}] (* L. Edson Jeffery, Feb 13 2015 *)
PROG
(Magma) [(5/4)*9^n-1/4: n in [0..20]]; // Vincenzo Librandi, Aug 09 2011
(PARI) Vec((1+x)/(1-10*x+9*x^2) + O(x^30)) \\ Michel Marcus, Feb 13 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Apr 02 2008
STATUS
approved