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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A244728 a(n) = 9*n^3.

Original entry on oeis.org

0, 9, 72, 243, 576, 1125, 1944, 3087, 4608, 6561, 9000, 11979, 15552, 19773, 24696, 30375, 36864, 44217, 52488, 61731, 72000, 83349, 95832, 109503, 124416, 140625, 158184, 177147, 197568, 219501, 243000, 268119, 294912, 323433, 353736, 385875, 419904
Offset: 0

Views

Author

Vincenzo Librandi, Jul 05 2014

Keywords

Comments

Volume of a pyramid (square base) with side and height 3*n. - Wesley Ivan Hurt, Aug 25 2014
Volume of the smallest square cuboid containing a ring torus where the tube and hole diameters are both n. - Torlach Rush, Jun 04 2019

Crossrefs

Cf. similar sequences listed in A244725.
Cf. A287335 (see Crossrefs).

Programs

  • GAP
    List([0..40], n-> 9*n^3); # G. C. Greubel, Jun 30 2019
  • Magma
    [9*n^3: n in [0..40]];
    
  • Magma
    I:=[0,9,72,243]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..40]];
    
  • Maple
    A244728:=n->9*n^3: seq(A244728(n), n=0..40); # Wesley Ivan Hurt, Aug 25 2014
  • Mathematica
    Table[9n^3, {n,0,40}] (* or *) CoefficientList[Series[9*x*(1+4*x+x^2)/(1- x)^4, {x,0,40}], x]
  • PARI
    vector(40, n, n--; 9*n^3) \\ G. C. Greubel, Jun 30 2019
    
  • Sage
    [9*n^3 for n in (0..40)] # G. C. Greubel, Jun 30 2019
    

Formula

G.f.: 9*x*(1 + 4*x + x^2)/(1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>3.
E.g.f.: 9*x*(1 + 3*x + x^2)*exp(x). - G. C. Greubel, Jun 30 2019

A121628 Nonnegative k such that 3*k + 1 is a perfect cube.

Original entry on oeis.org

0, 21, 114, 333, 732, 1365, 2286, 3549, 5208, 7317, 9930, 13101, 16884, 21333, 26502, 32445, 39216, 46869, 55458, 65037, 75660, 87381, 100254, 114333, 129672, 146325, 164346, 183789, 204708, 227157, 251190, 276861, 304224, 333333, 364242, 397005
Offset: 1

Views

Author

Zak Seidov, Aug 12 2006

Keywords

Comments

Intersection of this sequence and A001082 is {0, 21, 1365, 87381,...} all of the form (2^(6*m)-1)/3.

Crossrefs

Cf. A001082: 3*m + 1 is a perfect square.
Cf. A287335 (see Crossrefs).

Programs

  • Magma
    [3*n*(1+3*n+3*n^2): n in [1..40]]; // Vincenzo Librandi, Apr 11 2012
  • Mathematica
    CoefficientList[Series[3 (7 + 10 x + x^2)/(1 - x)^4, {x, 0, 40}], x] (* Vincenzo Librandi, Apr 11 2012 *)
    LinearRecurrence[{4,-6,4,-1},{0,21,114,333},40] (* Harvey P. Dale, Mar 08 2018 *)

Formula

a(n) = 3*(n - 1)*(3*n^2 - 3*n + 1) with n>0. Corresponding cubes are 3*a(n) + 1 = (3*n - 2)^3.
G.f.: 3*x^2*(7 + 10*x + x^2)/(1-x)^4. - Colin Barker, Apr 11 2012

Extensions

0 added and b-file updated by Bruno Berselli, May 23 2017
Showing 1-2 of 2 results.