# A004021 (b-file synthesized from sequence entry) 0 1 1 372 2 768 3 5684 4 6144 5 28608 6 23040 7 91956 8 61440 9 224680 10 140544 11 458688 12 276480 13 358240 14 480768 15 1467188 16 798720 17 2329012 18 1251072 19 3590952 20 1843200