# A337291 (b-file synthesized from sequence entry) 1 4 2 12 3 60 4 364 5 2448 6 17556 7 131560 8 1017900 9 8069424 10 65204656 11 535070172 12 4446927732 13 37353738800 14 316621743480 15 2704784196240 16 23263187479980 17 201275443944432 18 1750651680235920 19 15298438066553776 20 134252511729576240 21 1182622941581590080