This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A089908 #23 Mar 26 2024 14:45:57 %S A089908 0,28,609,9555,130501,1654947,20049393,235493839,2704938285, %T A089908 30549382731,340493827177,3754938271623,41049382716069, %U A089908 445493827160515,4804938271604961,51549382716049407,550493827160493853 %N A089908 Sum of digits of numbers between 0 and (7/9)*(10^n-1). %C A089908 From a suggestion of _Yalcin Aktar_ %H A089908 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (22,-141,220,-100). %F A089908 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)). %F A089908 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 %Y A089908 Cf. A089903, A089904, A089905, A087330, A089906, A089907, A089909, A034967. %K A089908 nonn,base,easy %O A089908 0,2 %A A089908 _Benoit Cloitre_, Nov 14 2003