# A013333 (b-file synthesized from sequence entry) 0 0 1 1 2 0 3 2 4 -4 5 12 6 -120 7 128 8 -4464 9 6912 10 -206880 11 776800 12 -12788224 13 95713984 14 -1101528064 15 13091780224 16 -133871961344 17 2061579919104 18 -22144979338752 19 381671021731840 20 -4690276122840064 21 83860033272100864