# A002750 (b-file synthesized from sequence entry)
0 1
1 4
2 15
3 76
4 373
5 2676
6 17539
7 152860
8 1383561
9 14658148
10 143131351
11 2070738924
12 24754959805
13 341745565396
14 5260157782923
15 92358395065276
16 1377499388715409
17 27622124789948100
18 476285499100204831
19 10464946811144407948
20 222724531608924013701