A363689 Number of alternating sign matrices of size n which are indecomposable by direct and skew sums.

1, 1, 0, 1, 16, 257, 5636, 187432, 9956054, 867875816, 125861715682, 30575624363575, 12486657463326416, 8588874417105963246, 9960958211434474577452, 19489076635898035234022220, 64349049302453152886635937502, 358611453994361731825817399132622, 3373425033361375072576454177693810076

Offset: 0

Author

Ludovic Schwob, Jun 15 2023

Keywords

• nonn

Examples

			a(3) = 1 because the only ASM of size 3 indecomposable by direct and skew sums is
  [0  1 0]
  [1 -1 1]
  [0  1 0]
		

Crossrefs

Cf. A005130, A231498, A359856.

Formula

G.f.: 2*(2 - 1/ASM(x)) - ASM(x) where ASM(x) is the g.f. of A005130.