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%I #27 Jan 21 2022 05:04:38
%S 0,1,2,3,4,5,6,8,16,24,32,40,48,57,114,171,228,285,342,400,800,1200,
%T 1600,2000,2400,2801,5602,8403,11204,14005,16806,19608,39216,58824,
%U 78432,98040,117648,137257,274514,411771,549028,686285,823542,960800
%N Numbers that are repdigits in base 7.
%H Vincenzo Librandi, <a href="/A048332/b048332.txt">Table of n, a(n) for n = 0..600</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Repdigit.html">Repdigit</a>.
%H <a href="/index/Rec#order_12">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,8,0,0,0,0,0,-7).
%F From _Chai Wah Wu_, May 30 2016: (Start)
%F a(n) = 8*a(n-6) - 7*a(n-12) for n > 11.
%F G.f.: x*(6*x^5 + 5*x^4 + 4*x^3 + 3*x^2 + 2*x + 1)/(7*x^12 - 8*x^6 + 1). (End)
%F a(n) = (n - 6*floor((n-1)/6))*(7^floor((n+5)/6) - 1)/6. - _Ilya Gutkovskiy_, May 30 2016
%F Sum_{n>=1} 1/a(n) = (147/10) * A248724 = 2.80637791743084519957... - _Amiram Eldar_, Jan 21 2022
%t Union[Flatten[Table[FromDigits[PadRight[{}, n, d], 7], {n, 0, 40}, {d, 6}]]] (* _Vincenzo Librandi_, Feb 06 2014 *)
%t LinearRecurrence[{0,0,0,0,0,8,0,0,0,0,0,-7},{0, 1, 2, 3, 4, 5, 6, 8, 16, 24, 32, 40}, 25] (* _G. C. Greubel_, May 30 2016 *)
%o (Python)
%o A048332_list = [0] + [int(d*l,7) for l in range(1,10) for d in '123456'] # _Chai Wah Wu_, May 30 2016
%Y Cf. A010785, A033020, A028987, A028988, A248724.
%K nonn,base,easy
%O 0,3
%A _Patrick De Geest_, Feb 15 1999
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