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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A376484 Array read by ascending antidiagonals: A(n,k)=4^k*Sum_{j=1..n} sin(2*j*Pi/(2*n+1))^(2*k).

Original entry on oeis.org

0, 1, 0, 2, 3, 0, 3, 5, 9, 0, 4, 7, 15, 27, 0, 5, 9, 21, 50, 81, 0, 6, 11, 27, 70, 175, 243, 0, 7, 13, 33, 90, 245, 625, 729, 0, 8, 15, 39, 110, 315, 882, 2250, 2187, 0, 9, 17, 45, 130, 385, 1134, 3234, 8125, 6561, 0, 10, 19, 51, 150, 455, 1386, 4158, 12005, 29375, 19683, 0
Offset: 0

Views

Author

Cheng-Jun Li, Sep 24 2024

Keywords

Comments

It is only a conjecture that A(n,k) is always an integer.
It appears that A(n,k) is divisible by 2*n+1 when n, k are positive integers.

Examples

			For n = 0 to 10 and k = 0 to 10, A(n, k) shows as below :
  0  0  0   0   0    0    0     0      0      0       0
  1  3  9  27  81  243  729  2187   6561  19683   59049
  2  5 15  50 175  625 2250  8125  29375 106250  384375
  3  7 21  70 245  882 3234 12005  44933 169099  638666
  4  9 27  90 315 1134 4158 15444  57915 218781  831222
  5 11 33 110 385 1386 5082 18876  70785 267410 1016158
  6 13 39 130 455 1638 6006 22308  83655 316030 1200914
  7 15 45 150 525 1890 6930 25740  96525 364650 1385670
  8 17 51 170 595 2142 7854 29172 109395 413270 1570426
  9 19 57 190 665 2394 8778 32604 122265 461890 1755182
 10 21 63 210 735 2646 9702 36036 135135 510510 1939938
		

Crossrefs

Conjectures: This array is related to existing sequences as follows: (Start)
Rows: A000004, A000244, A020876, A322459 (with alternate signs).
Columns: A001477, A005408, A016945.
Main Diagonals: A033876.
A(0,k) = A000004, A(1,k) = A000244, A(2,k) = A020876, A(3,k) = (-1)^k * A322459 (First 4 rows of the array).
A(n,0) = A001477(n > 0), A(n,1) = A005408(n > 0), A(n,2) = A016945(n > 0) (First 3 columns of the array).
A(n,n) = A033876(n > 0) (Main diagonal from top left corner). (End)

Programs

  • PARI
    A(n,k) = 4^k*sum(j=1,n,(sin(2*j*Pi/(2*n+1)))^(2*k))
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