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A010785
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Repdigit numbers, or numbers with repeated digits.
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99
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 111, 222, 333, 444, 555, 666, 777, 888, 999, 1111, 2222, 3333, 4444, 5555, 6666, 7777, 8888, 9999, 11111, 22222, 33333, 44444, 55555, 66666, 77777, 88888, 99999, 111111, 222222, 333333, 444444, 555555, 666666
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OFFSET
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0,3
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COMMENTS
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A037904(a(n)) = 0. - Reinhard Zumkeller, Dec 14 2007
Complement of A139819. - David Wasserman, May 21 2008
Subsequence of A134336 and of A178403; A178401(a(n))>0. - Reinhard Zumkeller, May 27 2010
For n > 0: A193459(a(n)) = A000005(a(n)), subsequence of A193460;
for n > 10: a(n) mod 10 = floor(a(n)/10) mod 10, A010879(n)=A010879(A059995(n)). - Reinhard Zumkeller, Jul 26 2011
A202022(a(n)) = 1. - Reinhard Zumkeller, Dec 09 2011
A151949(a(n)) = 0; A180410(a(n)) = A227362(a(n)). - Reinhard Zumkeller, Jul 09 2013
A047842(a(n)) = A244112(a(n)). - Reinhard Zumkeller, Nov 11 2014
Intersection of A009994 and A009996. - David F. Marrs, Sep 29 2018
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REFERENCES
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Bir Kafle et al., Triangular repblocks, Fib. Q., 56:4 (2018), 325-328.
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LINKS
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Reinhard Zumkeller, Table of n, a(n) for n = 0..1000
Bart Goddard, Jeremy Rouse, Sum of two repdigits a square, arXiv:1607.06681 [math.NT], 2016. Mentions this sequence.
Eric Weisstein's World of Mathematics, Repdigit
Wikipedia, Repdigit
Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 11, 0, 0, 0, 0, 0, 0, 0, 0, -10).
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FORMULA
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a(0)=0, a(1)=1, a(2)=2, a(3)=3, a(4)=4, a(5)=5, a(6)=6, a(7)=7, a(8)=8, a(9)=9, a(10)=11, a(11)=22, a(12)=33, a(13)=44, a(14)=55, a(15)=66, a(16)=77, a(17)=88, a(n)=11*a(n-9)-10*a(n-18). - Harvey P. Dale, Dec 28 2011
a(n) = (n-9*floor((n-1)/9))*(10^floor((n+8)/9)-1)/9. - José de Jesús Camacho Medina, Nov 06 2014
G.f.: x*(9*x^8+8*x^7+7*x^6+6*x^5+5*x^4+4*x^3+3*x^2+2*x+1)/((x^9-1)*(10*x^9-1)). - Robert Israel, Nov 09 2014
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MAPLE
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A010785 := proc(n)
(n-9*floor(((n-1)/9)))*((10^(floor(((n+8)/9)))-1)/9) ;
end proc:
seq(A010785(n), n = 0 .. 100); # Robert Israel, Nov 09 2014
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MATHEMATICA
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fQ[n_]:=Module[{id=IntegerDigits[n]}, Length[Union[id]]==1]; Select[Range[0, 10000], fQ] (* Vladimir Joseph Stephan Orlovsky, Dec 29 2010 *)
Union[FromDigits/@Flatten[Table[PadRight[{}, i, n], {n, 0, 9}, {i, 6}], 1]] (* or *) LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 0, 11, 0, 0, 0, 0, 0, 0, 0, 0, -10}, {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88}, 40] (* Harvey P. Dale, Dec 28 2011 *)
Union@ Flatten@ Table[k (10^n - 1)/9, {k, 0, 9}, {n, 6}] (* Robert G. Wilson v, Oct 09 2014 *)
Table[(n - 9 Floor[(n - 1)/9]) (10^Floor[(n + 8)/9] - 1)/9, {n, 0, 50}]
(* José de Jesús Camacho Medina, Nov 06 2014 *)
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PROG
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(PARI) a(n)=10^((n+8)\9)\9*((n-1)%9+1) \\ Charles R Greathouse IV, Jun 15 2011
(PARI) nxt(n, t=n%10)=if(t<9, n*(t+1), n*10+9))\t \\ Yields the term a(k+1) following a given term a(k)=n. M. F. Hasler, Jun 24 2016
(PARI) is(n)={1==#Set(digits(n))}
inv(n) = 9*#Str(n) + n%10 - 9 \\ David A. Corneth, Jun 24 2016
(Haskell)
a010785 n = a010785_list !! n
a010785_list = 0 : r [1..9] where
r (x:xs) = x : r (xs ++ [10*x + x `mod` 10])
-- Reinhard Zumkeller, Jul 26 2011
(MAGMA) [(n-9*Floor((n-1)/9))*(10^Floor((n+8)/9)-1)/9: n in [0..50]]; // Vincenzo Librandi, Nov 10 2014
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CROSSREFS
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Cf. A047842, A244112.
Sequence in context: A160818 A244514 A082810 * A032573 A190217 A222620
Adjacent sequences: A010782 A010783 A010784 * A010786 A010787 A010788
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KEYWORD
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nonn,base,easy,nice
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AUTHOR
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N. J. A. Sloane
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STATUS
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approved
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