400400

Appears in sequences

• Number of ways to place a non-attacking white and black queen on n X n chessboard.at n=25A035291
• a(n) = A081470(n)/n.at n=8A081471
• Numbers whose decimal expansion contains only 0's and 4's.at n=36A169967
• a(n) = concatenation of n^2 with itself.at n=19A253445
• T(n, k) = Sum_{j=0..k} (-1)^j*binomial(2*k, j)*(k - j)^(2*n)/(k!)^2, triangle read by rows, n >= 0 and 0 <= k <= n.at n=32A304336
• G.f. A(x,y) satisfies: A(x,y) + A(1/x,y) = Sum_{m>=0} (x^m + y + 1/x^m)^m, ignoring the infinite constant term; this is the triangle, read by rows, of coefficients T(n,k) of x^n*y^k in A(x,y) for n >= 1, k = 0..n-1.at n=129A316590
• Number T(n,k) of partitions of [n] having exactly k blocks of size at least three; triangle T(n,k), n>=0, 0<=k<=floor(n/3), read by rows.at n=39A355144