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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A341927 Bisection of the numerators of the convergents of cf(1,4,1,6,1,6,...,6,1).

Original entry on oeis.org

1, 6, 47, 370, 2913, 22934, 180559, 1421538, 11191745, 88112422, 693707631, 5461548626, 42998681377, 338527902390, 2665224537743, 20983268399554, 165200922658689, 1300624112869958, 10239791980300975, 80617711729537842, 634701901856001761, 4996997503118476246, 39341278123091808207
Offset: 0

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Author

John O. Oladokun, Feb 23 2021

Keywords

Comments

15*a(n)^2 - 11 is a square for all terms.
x = a(n) and y = a(n+1) satisfy x^2 + y^2 - 8*x*y = -11.
x = a(n) and y = a(n+2) satisfy x^2 + y^2 - 62*x*y = -704.

Examples

			a(3) = 8*6 - 1 = 47.
		

Crossrefs

Bisection of A237262.
Cf. A341929.

Programs

  • Mathematica
    LinearRecurrence[{8, -1}, {1,6},15]
  • PARI
    my(p=Mod('x,'x^2-8*'x+1)); a(n) = subst(lift(p^n),'x,6); \\ Kevin Ryde, Mar 01 2021

Formula

a(0) = 1; a(1) = 6; a(n) = 8*a(n-1) - a(n-2).
G.f.: (1 - 2*x)/(1 - 8*x + x^2). - Stefano Spezia, Feb 26 2021
a(n) = A237262(2*n + 1).
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