# A005756 (b-file synthesized from sequence entry) 2 4 3 24 4 304 5 5440 6 125824 7 3566080 8 119614464 9 4633387008 10 203524112384 11 9995546722304 12 542730361241600 13 32281981804347392 14 2087454641985945600 15 145797871819529650176 16 10938609224992417644544 17 877346430770422497673216