# A056267 (b-file synthesized from sequence entry) 1 0 2 2 3 6 4 12 5 30 6 54 7 126 8 240 9 504 10 990 11 2046 12 4020 13 8190 14 16254 15 32730 16 65280 17 131070 18 261576 19 524286 20 1047540 21 2097018 22 4192254 23 8388606 24 16772880 25 33554400 26 67100670 27 134217216 28 268419060 29 536870910 30 1073708010 31 2147483646