A089908 - OEIS

A089908

Sum of digits of numbers between 0 and (7/9)*(10^n-1).

0, 28, 609, 9555, 130501, 1654947, 20049393, 235493839, 2704938285, 30549382731, 340493827177, 3754938271623, 41049382716069, 445493827160515, 4804938271604961, 51549382716049407, 550493827160493853

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OFFSET

0,2

COMMENTS

From a suggestion of Yalcin Aktar

LINKS

Table of n, a(n) for n=0..16.

Index entries for linear recurrences with constant coefficients, signature (22,-141,220,-100).

FORMULA

a(n) = s(7, 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) = (7*(-22*(-1+10^n)+9*(4+9*10^n)*n))/162. G.f.: 7*x*(15*x^2-x+4) / ((x-1)^2*(10*x-1)^2). - Colin Barker, Jun 14 2013

CROSSREFS

Cf. A089903, A089904, A089905, A087330, A089906, A089907, A089909, A034967.

Sequence in context: A264459 A004371 A283096 * A038121 A240684 A184329

Adjacent sequences: A089905 A089906 A089907 * A089909 A089910 A089911

KEYWORD

nonn,base,easy

AUTHOR

Benoit Cloitre, Nov 14 2003

STATUS

approved