# A005490 (b-file synthesized from sequence entry) 1 1 2 4 3 13 4 44 5 163 6 666 7 2985 8 14550 9 76497 10 430746 11 2582447 12 16403028 13 109918745 14 774289168 15 5715471605 16 44087879136 17 354521950931 18 2965359744446 19 25749723493073 20 231719153184018 21 2157494726318233 22 20753996174222510 23 205985762120971167 24 2106795754056142536