Column 1 of triangle A128564; a(n) equals the number of permutations of {1..n+2} with [n/2+1] inversions for n>=0.
A128565
Column 1 of triangle A128564; a(n) equals the number of permutations of {1..n+2} with [n/2+1] inversions for n>=0.
Terms
- a(0) =1a(1) =2a(2) =5a(3) =9a(4) =29a(5) =49a(6) =174a(7) =285a(8) =1068a(9) =1717a(10) =6655a(11) =10569a(12) =41926a(13) =66013a(14) =266338a(15) =416687a(16) =1703027a(17) =2651355a(18) =10947079a(19) =16976806a(20) =70673825a(21) =109256095a(22) =457927079a(23) =706071989a(24) =2976282415a(25) =4579020513a(26) =19395654894a(27) =29784426945a(28) =126688273871a(29) =194231327451
External references
- oeis: A128565