# A175596 (b-file synthesized from sequence entry) 1 1 2 3 3 9 4 54 5 162 6 1458 7 4374 8 43740 9 262440 10 2361960 11 7085880 12 127545840 13 382637520 14 3443737680 15 30993639120 16 464904586800 17 1394713760400 18 25104847687200 19 75314543061600 20 1355661775108800 21 12200955975979200 22 109808603783812800 23 329425811351438400 24 9882774340543152000 25 59296646043258912000 26 533669814389330208000 27 5336698143893302080000 28 96060566590079437440000 29 288181699770238312320000 30 7780905893796434432640000