141680

Appears in sequences

• a(n) = n*(n-1)*(n-2)*(3*n-2)/6.at n=24A096200
• Numbers k not divisible by 6 such that sigma(k) > 3*k.at n=9A126104
• If X_1,...,X_n is a partition of a 2n-set X into 2-blocks then a(n) is equal to the number of 4-subsets of X containing none of X_i, (i=1,...,n).at n=19A130810
• Number of ways to place 2 nonattacking amazons (superqueens) on an n X n board.at n=23A172200
• Number of n-step self-avoiding walks on a line, where step X skips X - 1 spaces.at n=23A175941
• Exponential Riordan array (e^(mx),x*A000108(x)), m=2.at n=31A185947
• Number of (n+1)X(6+1) 0..2 arrays with the upper median of every 2X2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=12A237635
• Triangle read by rows: T(n,k) is the number of single loop solutions formed by n proper arches (connecting odd vertices to even vertices in the range 1 to 2n) above the x axis, k of which connect an odd vertex to a higher even vertex, with a rainbow of n arches below the x axis.at n=50A244312
• Number of bracelets (turnover necklaces) of length n that have no reflection symmetry and consist of 6 white beads and n-6 black beads.at n=40A308401
• G.f. A(x) satisfies A(x) = 1 + x^4*(1+x)*A(x)^4.at n=27A376546
• The least totient number k with exactly n solutions to the equation phi(x) = k, where all the solutions are nontotient numbers (A007617).at n=25A378510
• Expansion of 1/sqrt((1-x^3)^2 - 4*x^4).at n=31A383571