This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A281293 #20 Jan 27 2017 13:35:51 %S A281293 1,0,3,0,3,6,0,3,15,10,0,3,27,45,15,0,3,42,126,105,21,0,3,60,280,420, %T A281293 210,28,0,3,81,540,1260,1134,378,36,0,3,105,945,3150,4410,2646,630,45, %U A281293 0,3,132,1540,6930,13860,12936,5544,990,55,0,3,162,2376,13860,37422,49896,33264,10692,1485,66 %N A281293 Triangular array of generalized Narayana Numbers T(n,k) = 3*binomial(n+1,k)* binomial(n-3,k-1)/(n+1) for n >= 2 and 0 <= k <= n-2, read by rows. %C A281293 The current array is the case m = 2 of the generalized Narayana numbers N_m(n,k) := (m+1)/(n+1)*binomial(n+1,k)*binomial(n-m-1,k-1) for m >= 0, n >= m and 0 <= k <= n-m with N_m(n,0) = A000007(n-m). Case m = 0 gives the table of Narayana numbers A001263 without leading column N_0(n,0) = A000007(n). For m = 1 see A281260, and for m = 3 see A281297. %H A281293 David Callan, <a href="/A281260/a281260.pdf">Generalized Narayana Numbers</a> %F A281293 Row sums are A033184(n+1,3). %e A281293 The triangle begins: %e A281293 n\k: 0 1 2 3 4 5 6 7 8 9 10 11 ... %e A281293 02 : 1 %e A281293 03 : 0 3 %e A281293 04 : 0 3 6 %e A281293 05 : 0 3 15 10 %e A281293 06 : 0 3 27 45 15 %e A281293 07 : 0 3 42 126 105 21 %e A281293 08 : 0 3 60 280 420 210 28 %e A281293 09 : 0 3 81 540 1260 1134 378 36 %e A281293 10 : 0 3 105 945 3150 4410 2646 630 45 %e A281293 11 : 0 3 132 1540 6930 13860 12936 5544 990 55 %e A281293 12 : 0 3 162 2376 13860 37422 49896 33264 10692 1485 66 %e A281293 13 : 0 3 195 3510 25740 90090 162162 154440 77220 19305 2145 78 %e A281293 etc. %t A281293 Table[3 Binomial[n + 1, k] Binomial[n - 3, k - 1]/(n + 1), {n, 2, 12}, {k, 0, n - 2}] // Flatten (* _Michael De Vlieger_, Jan 19 2017 *) %Y A281293 Cf. A000007, A001263, A033184, A281260, A281297. %K A281293 nonn,tabl,easy %O A281293 2,3 %A A281293 _Werner Schulte_, Jan 19 2017