# A274520 (b-file synthesized from sequence entry) 0 0 1 2 2 4 3 20 4 64 5 248 6 880 7 3248 8 11776 9 43040 10 156736 11 571712 12 2083840 13 7597952 14 27698944 15 100985600 16 368164864 17 1342243328 18 4893475840 19 17840411648 20 65041678336 21 237125826560 22 864501723136 23 3151758405632 24 11490527150080 25 41891604733952 26 152726372368384