A293857 - cp's OEIS frontend

A293857 a(n) is the number of permutations {c_1..c_n} of {1..n} for which c_1 - c_2 + ... + (-1)^(n-1)*c_n are squares.

n	a(n)
0	1
1	1
2	1
3	4
4	12
5	36
6	144
7	1440
8	9216
9	66240
10	504000
11	7344000
12	73612800
13	830995200
14	9373190400
15	181875456000
16	2474319052800
17	38246274662400
18	572552876851200
19	13783143886848000
20	237527801118720000
21	4658378696294400000
22	86818505051013120000
23	2488457229932298240000

[1, 1, 1, 4, 12, 36, 144, 1440, 9216, 66240, 504000, 7344000, 73612800, 830995200, 9373190400, 181875456000, 2474319052800, 38246274662400, 572552876851200, 13783143886848000, 237527801118720000, 4658378696294400000, 86818505051013120000, 2488457229932298240000]

cp's OEIS Frontend

A293857 a(n) is the number of permutations {c_1..c_n} of {1..n} for which c_1 - c_2 + ... + (-1)^(n-1)*c_n are squares.

Table of values

List of values