cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A272576 a(n) = f(10, f(9, n)), where f(k,m) = floor(m*k/(k-1)).

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 20, 21, 22, 23, 24, 25, 26, 27, 30, 31, 32, 33, 34, 35, 36, 37, 40, 41, 42, 43, 44, 45, 46, 47, 50, 51, 52, 53, 54, 55, 56, 57, 60, 61, 62, 63, 64, 65, 66, 67, 70, 71, 72, 73, 74, 75, 76, 77, 80, 81, 82, 83, 84, 85, 86, 87, 90
Offset: 0

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Author

Bruno Berselli, May 03 2016

Keywords

Comments

Also, numbers not ending with the digit 8 or 9.
The initial terms coincide with those of A007094 and A039155. First disagreement is after 77 (index 63): a(64) = 80, A007094(64) = 100 and A039155(65) = 89.

Crossrefs

Cf. similar sequences listed in A272574.

Programs

  • Magma
    k:=10; f:=func; [f(k,f(k-1,n)): n in [0..70]];
    
  • Maple
    f := (k, m) -> floor(m*k/(k-1)):
    a := n -> f(10, f(9,n)):
    seq(a(n), n = 0..72); # Peter Luschny, May 03 2016
  • Mathematica
    f[k_, m_] := Floor[m*k/(k-1)];
    a[n_] := f[10, f[9, n]];
    Table[a[n], {n, 0, 72}] (* Jean-François Alcover, May 09 2016 *)
    LinearRecurrence[{1,0,0,0,0,0,0,1,-1},{0,1,2,3,4,5,6,7,10},90] (* Harvey P. Dale, Jun 22 2017 *)
  • PARI
    is(n)=n%10<8 \\ Charles R Greathouse IV, Feb 13 2017
  • Sage
    f = lambda k, m: floor(m*k/(k-1))
    a = lambda n: f(10, f(9, n))
    [a(n) for n in range(73)] # Peter Luschny, May 03 2016
    

Formula

G.f.: x*(1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + 3*x^7)/((1 + x)*(1 - x)^2*(1 + x^2) *(1 + x^4)).
a(n) = a(n-1) + a(n-8) - a(n-9).
a(n) = 1.25n + O(1). - Charles R Greathouse IV, Nov 07 2022
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