# A067980 (b-file synthesized from sequence entry) 0 3 1 13 2 31 3 69 4 140 5 274 6 519 7 963 8 1757 9 3165 10 5642 11 9972 12 17499 13 30521 14 52955 15 91461 16 157336 17 269702 18 460863 19 785295 20 1334713 21 2263293 22 3829846 23 6468264 24 10905075 25 18355429 26 30849559 27 51776133 28 86785892