# A005373 (b-file synthesized from sequence entry) 1 1 2 3 3 21 4 231 5 3495 6 67455 7 1584765 8 43897455 9 1400923755 10 50619052575 11 2042745514425 12 91066568444775 13 4444738893770175 14 235731740255186175 15 13499365993279291125 16 830161812269496081375 17 54564569247212367217875 18 3817309552613869238301375