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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A182456 a(0)=1; for n>0, a(n) = ( a(n-1) mod (n+3) )*(n+3).

Original entry on oeis.org

1, 4, 20, 12, 35, 24, 54, 40, 77, 60, 104, 84, 135, 112, 170, 144, 209, 180, 252, 220, 299, 264, 350, 312, 405, 364, 464, 420, 527, 480, 594, 544, 665, 612, 740, 684, 819, 760, 902, 840, 989, 924, 1080, 1012, 1175, 1104, 1274, 1200, 1377, 1300, 1484
Offset: 0

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Author

Alex Ratushnyak, Apr 30 2012

Keywords

Examples

			a(6) = (a(5) mod 9) * 9 = (24 mod 9) * 9 = 6*9 = 54.
		

Crossrefs

Cf. A182455.

Programs

  • Mathematica
    CoefficientList[Series[(-1 - 3*x - 14*x^2 + 14*x^3 + 8*x^4 - 8*x^5)/((x - 1)^3*(1 + x)^2), {x,0,50}], x] (* G. C. Greubel, Feb 25 2017 *)
    RecurrenceTable[{a[0]==1,a[n]==Mod[a[n-1],n+3](n+3)},a,{n,50}] (* Harvey P. Dale, Oct 21 2018 *)
  • PARI
    my(x='x+O('x^50)); Vec((-1-3*x-14*x^2+14*x^3+8*x^4-8*x^5)/((x-1)^3*(1+x)^2)) \\ G. C. Greubel, Feb 25 2017
  • Python
    a=1
    for n in range(1, 55):
        print(a, end=",")
        a = (a%(n+3)) * (n+3)
    

Formula

For k>0, a(2*k) = A182455(2*k+3)-1, a(2*k+1) = A182455(2*k).
From Alexander R. Povolotsky, May 01 2012: (Start)
for the same sequence with index starting from 1 instead of 0, i.e. k=1,2,...
a(k+1) = (k+3)^2 - (k+3)*a(k)/(k+2).
G.f.: (-1-3*x-14*x^2+14*x^3+8*x^4-8*x^5)/((x-1)^3*(1+x)^2). (End)
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