# A000641 (b-file synthesized from sequence entry) 0 0 1 1 2 2 3 5 4 14 5 39 6 109 7 312 8 890 9 2552 10 7325 11 21047 12 60465 13 173750 14 499068 15 1433071 16 4113105 17 11799780 18 33834367 19 96968462 20 277771344 21 795310628 22 2276055442 23 6510786627 24 18616389094 25 53207964655 26 152014267327 27 434136228215