Sum over all permutations without double ascents on n elements and each permutation contributes 2 raised to the power of the number of double descents.
A230071
Sum over all permutations without double ascents on n elements and each permutation contributes 2 raised to the power of the number of double descents.
Terms
- a(0) =0a(1) =0a(2) =2a(3) =6a(4) =26a(5) =130a(6) =782a(7) =5474a(8) =43794a(9) =394146a(10) =3941462a(11) =43356082a(12) =520272986a(13) =6763548818a(14) =94689683454
External references
- oeis: A230071