A005156 - cp's OEIS frontend

A005156 Number of alternating sign 2n+1 X 2n+1 matrices symmetric about the vertical axis (VSASM's); also 2n X 2n off-diagonally symmetric alternating sign matrices (OSASM's).

n	a(n)
0	1
1	1
2	3
3	26
4	646
5	45885
6	9304650
7	5382618660
8	8878734657276
9	41748486581283118
10	559463042542694360707
11	21363742267675013243931852
12	2324392978926652820310084179576
13	720494439459132215692530771292602232
14	636225819409712640497085074811372777428304

[1, 1, 3, 26, 646, 45885, 9304650, 5382618660, 8878734657276, 41748486581283118, 559463042542694360707, 21363742267675013243931852, 2324392978926652820310084179576, 720494439459132215692530771292602232, 636225819409712640497085074811372777428304]

cp's OEIS Frontend

A005156 Number of alternating sign 2n+1 X 2n+1 matrices symmetric about the vertical axis (VSASM's); also 2n X 2n off-diagonally symmetric alternating sign matrices (OSASM's).

Table of values

List of values