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 A064756 a(n) = n*10^n - 1. 4
 9, 199, 2999, 39999, 499999, 5999999, 69999999, 799999999, 8999999999, 99999999999, 1099999999999, 11999999999999, 129999999999999, 1399999999999999, 14999999999999999, 159999999999999999, 1699999999999999999, 17999999999999999999 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 Paul Leyland, Factors of Cullen and Woodall numbers Paul Leyland, Generalized Cullen and Woodall numbers Amelia Carolina Sparavigna, Some Groupoids and their Representations by Means of Integer Sequences, International Journal of Sciences (2019) Vol. 8, No. 10. Index entries for linear recurrences with constant coefficients, signature (21,-120,100). MAPLE 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 MATHEMATICA Array[# 10^# - 1 &, 18] (* Michael De Vlieger, Jan 14 2020 *) PROG (Magma) [ n*10^n-1: n in [1..20]]; // Vincenzo Librandi, Sep 16 2011 CROSSREFS 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). Sequence in context: A157594 A232276 A196910 * A197077 A093708 A052145 Adjacent sequences: A064753 A064754 A064755 * A064757 A064758 A064759 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Oct 19 2001 STATUS approved

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Last modified January 28 17:08 EST 2023. Contains 359895 sequences. (Running on oeis4.)