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%I #26 Sep 08 2022 08:45:04
%S 9,199,2999,39999,499999,5999999,69999999,799999999,8999999999,
%T 99999999999,1099999999999,11999999999999,129999999999999,
%U 1399999999999999,14999999999999999,159999999999999999,1699999999999999999,17999999999999999999
%N a(n) = n*10^n - 1.
%H Vincenzo Librandi, <a href="/A064756/b064756.txt">Table of n, a(n) for n = 1..1000</a>
%H Paul Leyland, <a href="https://web.archive.org/web/20120204131613/http://www.leyland.vispa.com/numth/factorization/cullen_woodall/cw.htm">Factors of Cullen and Woodall numbers</a>
%H Paul Leyland, <a href="https://web.archive.org/web/20120204131629/http://www.leyland.vispa.com/numth/factorization/cullen_woodall/gcw.htm">Generalized Cullen and Woodall numbers</a>
%H Amelia Carolina Sparavigna, <a href="https://doi.org/10.18483/ijSci.2188">Some Groupoids and their Representations by Means of Integer Sequences</a>, International Journal of Sciences (2019) Vol. 8, No. 10.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (21,-120,100).
%p k:= 10; f:= gfun:-rectoproc({1 + (k-1)*n + k*n*a(n-1) - (n-1)*a(n) = 0, a(1) = k-1}, a(n), remember): map(f, [$1..20]); # _Georg Fischer_, Feb 19 2021
%t Array[# 10^# - 1 &, 18] (* _Michael De Vlieger_, Jan 14 2020 *)
%o (Magma) [ n*10^n-1: n in [1..20]]; // _Vincenzo Librandi_, Sep 16 2011
%Y For a(n)=n*k^n-1 cf. -A000012 (k=0), A001477 (k=1), A003261 (k=2), A060352 (k=3), A060416 (k=4), A064751 (k=5), A064752 (k=6), A064753 (k=7), A064754 (k=8), A064755 (k=9), this sequence (k=10), A064757 (k=11), A064758 (k=12).
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_, Oct 19 2001
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