# A018103 (b-file synthesized from sequence entry) 0 1 1 2 2 4 3 9 4 20 5 42 6 89 7 189 8 400 9 846 10 1789 11 3783 12 8000 13 16918 14 35777 15 75659 16 160000 17 338359 18 715542 19 1513187 20 3200000 21 6767176 22 14310835 23 30263731 24 64000000 25 135343522 26 286216701 27 605274630 28 1280000000