Number of nX3 zero-sum -1..1 arrays with rows and columns lexicographically nondecreasing.

A202028

Number of nX3 zero-sum -1..1 arrays with rows and columns lexicographically nondecreasing.

Terms

    a(0) =2a(1) =21a(2) =181a(3) =1341a(4) =8312a(5) =44300a(6) =207562a(7) =872998a(8) =3348194a(9) =11857834a(10) =39165935a(11) =121628739a(12) =357500769a(13) =1000121700a(14) =2675524936a(15) =6872220036a(16) =17006979680a(17) =40673780258a(18) =94256429647a(19) =212145160692a(20) =464710684230a(21) =992576762139

External references