|
|
A089904
|
|
Sum of digits of numbers between 0 and (2/9)*(10^n-1).
|
|
6
|
|
|
0, 3, 109, 2055, 30501, 404947, 5049393, 60493839, 704938285, 8049382731, 90493827177, 1004938271623, 11049382716069, 120493827160515, 1304938271604961, 14049382716049407, 150493827160493853
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
COMMENTS
|
|
|
LINKS
|
|
|
FORMULA
|
a(n) = s(2, n-1) where s(a, k)=a*(k+1)+a^2*sum(i=0, k, i*10^(k-i))+sum(i=0, k, 5*a*(9*(k-i)+a- 1)*10^(k-i-1)).
a(n) = (-77*(-1+10^n)+9*(14+9*10^n)*n)/81. G.f.: x*(80*x^2+43*x+3) / ((x-1)^2*(10*x-1)^2). - Colin Barker, Jun 14 2013
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|