cp's OEIS Frontend

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.

A174450 Triangle T(n, k, q) = n!*(n+1)!*q^k/((n-k)!(n-k+1)!) if floor(n/2) > k-1, otherwise n!*(n+1)!*q^(n-k)/(k!*(k+1)!) for q = 2, read by rows.

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%I A174450 #11 Sep 08 2022 08:45:51
%S A174450 1,1,1,1,12,1,1,24,24,1,1,40,960,40,1,1,60,2400,2400,60,1,1,84,5040,
%T A174450 201600,5040,84,1,1,112,9408,564480,564480,9408,112,1,1,144,16128,
%U A174450 1354752,81285120,1354752,16128,144,1,1,180,25920,2903040,243855360,243855360,2903040,25920,180,1
%N A174450 Triangle T(n, k, q) = n!*(n+1)!*q^k/((n-k)!(n-k+1)!) if floor(n/2) > k-1, otherwise n!*(n+1)!*q^(n-k)/(k!*(k+1)!) for q = 2, read by rows.
%H A174450 G. C. Greubel, <a href="/A174450/b174450.txt">Rows n = 0..50 of the triangle, flattened</a>
%F A174450 T(n, k, q) = n!*(n+1)!*q^k/((n-k)!(n-k+1)!) if floor(n/2) > k-1, otherwise n!*(n+1)!*q^(n-k)/(k!*(k+1)!) for q = 2.
%F A174450 T(n, n-k, q) = T(n, k, q).
%F A174450 From _G. C. Greubel_, Nov 29 2021: (Start)
%F A174450 T(2*n, n, q) = q^n*(2*n+1)!*Catalan(n) for q = 2.
%F A174450 T(n, k, q) = binomial(n, k)*binomial(n+1, k+1) * ( k!*(k+1)!*q^k/(n-k+1) if (floor(n/2) >= k), otherwise ((n-k)!)^2*q^(n-k) ), for q = 2. (End)
%e A174450 Triangle begins as:
%e A174450   1;
%e A174450   1,   1;
%e A174450   1,  12,     1;
%e A174450   1,  24,    24,       1;
%e A174450   1,  40,   960,      40,         1;
%e A174450   1,  60,  2400,    2400,        60,         1;
%e A174450   1,  84,  5040,  201600,      5040,        84,       1;
%e A174450   1, 112,  9408,  564480,    564480,      9408,     112,     1;
%e A174450   1, 144, 16128, 1354752,  81285120,   1354752,   16128,   144,   1;
%e A174450   1, 180, 25920, 2903040, 243855360, 243855360, 2903040, 25920, 180,  1;
%t A174450 T[n_, k_, q_]:= If[Floor[n/2]>k-1, n!*(n+1)!*q^k/((n-k)!*(n-k+1)!), n!*(n+1)!*q^(n-k)/(k!*(k+1)!)];
%t A174450 Table[T[n, k, 2], {n,0,12}, {k,0,n}]//Flatten
%o A174450 (Magma)
%o A174450 F:= Factorial; // T = A174450
%o A174450 T:= func< n,k,q | Floor(n/2) gt k-1 select F(n)*F(n+1)*q^k/(F(n-k)*F(n-k+1)) else F(n)*F(n+1)*q^(n-k)/(F(k)*F(k+1)) >;
%o A174450 [T(n,k,2): k in [0..n], n in [0..12]]; // _G. C. Greubel_, Nov 29 2021
%o A174450 (Sage)
%o A174450 f=factorial
%o A174450 def A174450(n,k,q):
%o A174450     if ((n//2)>k-1): return f(n)*f(n+1)*q^k/(f(n-k)*f(n-k+1))
%o A174450     else: return f(n)*f(n+1)*q^(n-k)/(f(k)*f(k+1))
%o A174450 flatten([[A174450(n,k,2) for k in (0..n)] for n in (0..12)]) # _G. C. Greubel_, Nov 29 2021
%Y A174450 Cf. A174449 (q=1), this sequence (q=2), A174451 (q=3).
%Y A174450 Cf. A000108.
%K A174450 nonn,tabl,easy
%O A174450 0,5
%A A174450 _Roger L. Bagula_, Mar 20 2010
%E A174450 Edited by _G. C. Greubel_, Nov 29 2021