# A073983 (b-file synthesized from sequence entry) 1 1 2 2 3 3 4 18 5 180 6 1296 7 8100 8 50544 9 297432 10 1679616 11 9722592 12 58576608 13 358108128 14 2179768320 15 13162730688 16 78976384128 17 472093588224 18 2821109907456 19 16891882995456 20 101356447675392 21 608764662139392 22 3656158440062976 23 21947538146863104 24 131685972252346368