Triangle read by rows: T(n,k) is the number of permutations of [n] having k-1 alternating descents (1<=k<=n). The index i is an alternating descent of a permutation p if either i is odd and p(i)>p(i+1), or i is even and p(i)<p(i+1).

A145876

Triangle read by rows: T(n,k) is the number of permutations of [n] having k-1 alternating descents (1<=k<=n). The index i is an alternating descent of a permutation p if either i is odd and p(i)>p(i+1), or i is even and p(i)<p(i+1).

Terms

    a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =2a(6) =5a(7) =7a(8) =7a(9) =5a(10) =16a(11) =26a(12) =36a(13) =26a(14) =16a(15) =61a(16) =117a(17) =182a(18) =182a(19) =117a(20) =61a(21) =272a(22) =594a(23) =1056a(24) =1196a(25) =1056a(26) =594a(27) =272a(28) =1385a(29) =3407

External references