# A026995 (b-file synthesized from sequence entry) 0 1 1 3 2 8 3 20 4 54 5 147 6 368 7 873 8 2150 9 5401 10 12948 11 29952 12 71386 13 173370 14 406720 15 928013 16 2173248 17 5178906 18 11994740 19 27138972 20 62859236 21 147973950 22 339831168 23 764579850 24 1757600988 25 4102109109 26 9364407584 27 20984799649