# A124023 (b-file synthesized from sequence entry) 0 1 1 2 2 10 3 28 4 108 5 344 6 1224 7 4080 8 14128 9 47840 10 164128 11 558784 12 1910976 13 6518144 14 22267008 15 75998976 16 259527424 17 885980672 18 3025129984 19 10328034304 20 35262925824 21 120393537536 22 411052492800 23 1403414507520 24 4791569821696 25 16359416717312 26 55854594334720