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.

Showing 1-4 of 4 results.

A049013 Duplicate of A020735.

Original entry on oeis.org

5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51
Offset: 1

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Author

Keywords

A144396 The odd numbers greater than 1.

Original entry on oeis.org

3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133
Offset: 1

Views

Author

Paul Curtz, Oct 03 2008

Keywords

Comments

Last number of the n-th row of the triangle described in A142717.
If negated, these are also the values at local minima of the sequence A141620.
a(n) is the shortest leg of the n-th Pythagorean triple with consecutive longer leg and hypotenuse. The n-th such triple is given by (2n+1,2n^2+2n, 2n^2+2n+1), so that the longer legs are A046092(n) and the hypotenuses are A099776(n). - Ant King, Feb 10 2011
Numbers k such that the symmetric representation of sigma(k) has a pair of bars as its ends (cf. A237593). - Omar E. Pol, Sep 28 2018
Numbers k such that there is a prime knot with k crossings and braid index 2. (IS this true with "prime" removed?) - Charles R Greathouse IV, Feb 14 2023

Crossrefs

Complement of A004275 and of A004277.
Essentially the same as A140139, A130773, A062545, A020735, A005818.

Programs

Formula

a(n) = A005408(n+1) = A000290(n+1) - A000290(n).
G.f.: x*(3-x)/(1-x)^2. - Jaume Oliver Lafont, Aug 30 2009
a(n) = A254858(n-1,2). - Reinhard Zumkeller, Feb 09 2015

Extensions

Edited by R. J. Mathar, May 21 2009

A020742 Pisot sequence T(7,9).

Original entry on oeis.org

7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139
Offset: 0

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Author

Keywords

Crossrefs

Subsequence of A005408, A020735. See A008776 for definitions of Pisot sequences.
Essentially the same as A005818.

Programs

  • Mathematica
    T[x_, y_, z_] := Block[{a}, a[0] = x; a[1] = y; a[n_] := a[n] = Floor[a[n - 1]^2/a[n - 2]]; Table[a[n], {n, 0, z}]]; T[7, 9, 66] (* Michael De Vlieger, Aug 08 2016 *)
  • PARI
    pisotT(nmax, a1, a2) = {
      a=vector(nmax); a[1]=a1; a[2]=a2;
      for(n=3, nmax, a[n] = floor(a[n-1]^2/a[n-2]));
      a
    }
    pisotT(50, 7, 9) \\ Colin Barker, Aug 08 2016

Formula

a(n) = 2*n + 7.
a(n) = 2*a(n-1) - a(n-2).
From Elmo R. Oliveira, Oct 30 2024: (Start)
G.f.: (7 - 5*x)/(1 - x)^2.
E.g.f.: (7 + 2*x)*exp(x).
a(n) = A016825(n+3)/2 = A028560(n+1) - A028560(n). (End)

A069476 First differences of A069475, successive differences of (n+1)^6-n^6.

Original entry on oeis.org

1800, 2520, 3240, 3960, 4680, 5400, 6120, 6840, 7560, 8280, 9000, 9720, 10440, 11160, 11880, 12600, 13320, 14040, 14760, 15480, 16200, 16920, 17640, 18360, 19080, 19800, 20520, 21240, 21960, 22680, 23400, 24120, 24840, 25560, 26280, 27000
Offset: 0

Views

Author

Eli McGowan (ejmcgowa(AT)mail.lakeheadu.ca), Mar 26 2002

Keywords

Crossrefs

Programs

  • Mathematica
    Table[720 n + 1800, {n, 0, 40}] (* Bruno Berselli, Feb 25 2015 *)

Formula

a(n) = 720*n + 1800 = 360*A020735(n+1).
G.f.: 360*(5 - 3*x)/(1 - x)^2. [Bruno Berselli, Feb 25 2015]

Extensions

Offset changed from 1 to 0 and added a(0)=1800 by Bruno Berselli, Feb 25 2015
Showing 1-4 of 4 results.