A091686 - OEIS

%I #11 May 27 2026 10:37:07

%S 1,8,77,666,5555,44444,333333,2222222,11111111,0,-1111111111,

%T -22222222222,-333333333333,-4444444444444,-55555555555555,

%U -666666666666666,-7777777777777777,-88888888888888888,-999999999999999999,-11111111111111111110,-122222222222222222221

%N a(n) = 0^n + ((n-9)/9)*(1-10^n).

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (22,-141,220,-100).

%F a(n) = P(n, n+1, -10) where P(n, m, z) = Product_{k=0..n-1} (z - Sum_{j=1..m} w(n)^(j*k)), where w(n) = e^(2*Pi*i/n), i = sqrt(-1).

%o (PARI) a(n)=0^n+(n-9)/9*(1-10^n) \\ _Charles R Greathouse IV_, May 27 2026

%K sign,easy

%O 0,2

%A _Paul Barry_, Jan 29 2004