# A000645 (b-file synthesized from sequence entry) 0 1 1 2 2 4 3 10 4 25 5 64 6 166 7 437 8 1157 9 3087 10 8276 11 22287 12 60230 13 163284 14 443820 15 1209155 16 3300890 17 9027337 18 24727437 19 67829684 20 186302693 21 512301120 22 1410237805 23 3885803531 24 10716571591 25 29579231200 26 81704634803 27 225845362116