OFFSET
0,1
COMMENTS
Partial sums give 3, 36, 351, 3240, 29403,...: A026121.
a(n) is the sum of all integers having n+1 digits in their ternary expansion (without leading zeros). - Jonathan Vos Post, Sep 07 2006
LINKS
FORMULA
G.f.: 3*(1-x)/(1-12*x+27*x^2). [Bruno Berselli, Jun 11 2013]
a(n) = 3^(n-1)*(4*3^(n+1)-3). [Bruno Berselli, Jun 11 2013]
a(0)=3, a(1)=33, a(n)=12*a(n-1)-27*a(n-2). - Harvey P. Dale, Jun 19 2013
EXAMPLE
a(0) = 1+2 = 3,
a(1) = 3+4+5+6+7+8 = 33.
MATHEMATICA
Table[3^(n - 1) (4 3^(n + 1) - 3), {n, 0, 20}] (* Bruno Berselli, Jun 11 2013 *)
LinearRecurrence[{12, -27}, {3, 33}, 30] (* Harvey P. Dale, Jun 19 2013 *)
PROG
(PARI) a(n) = sum(i=3^n, 3^(n+1)-1, i) \\ Michel Marcus, Jun 11 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Michel Marcus, Jun 10 2013
STATUS
approved