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 1-3 of 3 results.

A027445 a(n) = n^4 + n^3 + n^2 + n^1.

Original entry on oeis.org

0, 4, 30, 120, 340, 780, 1554, 2800, 4680, 7380, 11110, 16104, 22620, 30940, 41370, 54240, 69904, 88740, 111150, 137560, 168420, 204204, 245410, 292560, 346200, 406900, 475254, 551880, 637420, 732540, 837930, 954304, 1082400, 1222980, 1376830, 1544760, 1727604
Offset: 0

Views

Author

Keywords

Comments

a(A047203(n)) mod 10 = 0; a(A016861(n)) mod 10 = 4. - Reinhard Zumkeller, Oct 23 2006

Crossrefs

Equals 2 * A071237(n).
Column k=4 of A228275.

Programs

A155121 a(n) = 2*n*(1 + n + n^2 + n^3) - 3.

Original entry on oeis.org

-3, 5, 57, 237, 677, 1557, 3105, 5597, 9357, 14757, 22217, 32205, 45237, 61877, 82737, 108477, 139805, 177477, 222297, 275117, 336837, 408405, 490817, 585117, 692397, 813797, 950505, 1103757, 1274837, 1465077, 1675857
Offset: 0

Views

Author

Roger L. Bagula, Jan 20 2009

Keywords

Crossrefs

Programs

  • Magma
    [2*n*(1+n+n^2+n^3)-3: n in [0..40] ]; // Vincenzo Librandi, May 23 2011
    
  • Maple
    seq( -3 +2*n +2*n^2 +2*n^3 +2*n^4, n=0..40); # G. C. Greubel, Mar 25 2021
  • Mathematica
    Table[-3 +2n +2n^2 +2n^3 +2n^4, {n, 0, 30}]
  • Sage
    [-3 +2*n +2*n^2 +2*n^3 +2*n^4 for n in (0..40)] # G. C. Greubel, Mar 25 2021

Formula

a(n) = 2*n*(1 + n + n^2 + n^3) - 3.
G.f.: (3 - 20*x - 2*x^2 - 32*x^3 + 3*x^4)/(x-1)^5.
From Bruno Berselli, Dec 16 2010: (Start)
a(n) = 4*A071237(n) - 3.
a(n) = 2*A024003(n)/(1-n) - 5 (n>1). (End)
E.g.f.: (-3 + 8*x + 22*x^2 + 14*x^3 + 2*x^4)*exp(x). - G. C. Greubel, Mar 25 2021

A265129 Triangle read by rows, formed as the sum of the two versions of the natural numbers filling an equilateral triangle.

Original entry on oeis.org

2, 5, 5, 10, 10, 10, 17, 17, 17, 17, 26, 26, 26, 26, 26, 37, 37, 37, 37, 37, 37, 50, 50, 50, 50, 50, 50, 50, 65, 65, 65, 65, 65, 65, 65, 65, 82, 82, 82, 82, 82, 82, 82, 82, 82, 101, 101, 101, 101, 101, 101, 101, 101, 101, 101
Offset: 1

Views

Author

Craig Knecht, Dec 02 2015

Keywords

Comments

The natural numbers can sequentially fill a right- or left-handed equilateral triangle. Componentwise addition of the values of these two triangles produces the present triangle.
The row sums for this triangle give A034262.
The difference between the right- and left-handed triangles produces A049581.

Examples

			Displayed as a triangle:
   2;
   5  5;
  10 10 10;
  17 17 17 17;
  26 26 26 26 26;
  37 37 37 37 37 37;
  ...
		

Crossrefs

Column k=1 gives A002522.
Cf. A049581 (difference of triangles), A034262 (row sum of triangle), A069894 (center column).
Cf. A071237.

Programs

  • Maple
    seq(seq(n^2+1,k=1..n),n=1..10); # Georg Fischer, Oct 01 2021

Formula

T(n,k) = n^2 + 1 for k = 1..n and n >= 1. - Georg Fischer, Oct 01 2021
Sum_{k=1..n} k * T(n,k) = A071237(n). - Alois P. Heinz, Oct 01 2021

Extensions

Row 6 with T(6,k)=37 inserted by Georg Fischer, Oct 01 2021
Showing 1-3 of 3 results.