Triangle read by rows: T(n,k) is the number of ordered pairs of n-permutations with exactly k common double descents, n>=0, 0<=k<=max{0,n-2}.
A334257
Triangle read by rows: T(n,k) is the number of ordered pairs of n-permutations with exactly k common double descents, n>=0, 0<=k<=max{0,n-2}.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =35a(4) =1a(5) =545a(6) =30a(7) =1a(8) =13250a(9) =1101a(10) =48a(11) =1a(12) =463899a(13) =51474a(14) =2956a(15) =70a(16) =1a(17) =22106253a(18) =3070434a(19) =217271a(20) =7545a(21) =96a(22) =1a(23) =1375915620a(24) =229528818a(25) =19372881a(26) =864632a(27) =20322a(28) =126a(29) =1
External references
- oeis: A334257