# A227946 (b-file synthesized from sequence entry) 0 1 1 2 2 7 3 19 4 47 5 163 6 487 7 1307 8 2879 9 19683 10 39367 11 177147 12 531441 13 1594323 14 4782969 15 14348907 16 43046721 17 86093443 18 258280327 19 688747547 20 3486784401 21 10460353203