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.

A243209 Number of inequivalent (mod D_3) ways to place 4 points on a triangular grid of side n so that they are not vertices of an equilateral triangle with sides parallel to the grid.

Table of values

n a(n)
3 1
4 25
5 186
6 881
7 3146
8 9264
9 23810
10 55058
11 117205
12 233135
13 438544
14 786541
15 1354696
16 2252202
17 3630684
18 5694984
19 8718963
20 13060515
21 19184110
22 27681103
23 39300096
24 54974216
25 75861038
26 103377456
27 139251749
28 185567453
29 244828780
30 320015885
31 414665890
32 532940080

List of values

[1, 25, 186, 881, 3146, 9264, 23810, 55058, 117205, 233135, 438544, 786541, 1354696, 2252202, 3630684, 5694984, 8718963, 13060515, 19184110, 27681103, 39300096, 54974216, 75861038, 103377456, 139251749, 185567453, 244828780, 320015885, 414665890, 532940080]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.