21456

Appears in sequences

• Number of degree-n permutations of order dividing 12.at n=8A053502
• Numbers n such that 5*10^n-1 is prime.at n=16A056712
• The n-th n-gonal number: a(n) = n*(n^2 - 3*n + 4)/2.at n=36A060354
• Sums of members of groups in A076062.at n=34A076060
• Square table T, read by antidiagonals, where T(n,k) gives the number of n-th generation descendents of a node labeled (k) in the tree of tournament sequences.at n=61A093729
• Expansion of -2*x^2*(-3-2*x+x^2-x^3-2*x^4+x^5) / ( (1+x)^2*(x-1)^4 ).at n=35A178465
• Coefficient of x^2 in the reduction by (x^3 -> x + 1) of the polynomial F(n+1)*x^n, where F(n)=A000045 (Fibonacci sequence).at n=11A192913
• Row sums of A204087.at n=17A204088
• Number of (n+1) X (1+1) 0..2 arrays with the maximum plus the upper median plus the minimum of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=4A237405
• Number of (n+1) X (5+1) 0..2 arrays with the maximum plus the upper median plus the minimum of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=0A237409
• T(n,k)=Number of (n+1) X (k+1) 0..2 arrays with the maximum plus the upper median plus the minimum of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=10A237412
• T(n,k)=Number of (n+1) X (k+1) 0..2 arrays with the maximum plus the upper median plus the minimum of every 2 X 2 subblock differing from its horizontal and vertical neighbors by exactly one.at n=14A237412
• Numbers n such that the sum of n consecutive positive cubes is a cube for some initial starting number k.at n=31A240970
• 36-gonal numbers: a(n) = n*(17*n-16).at n=36A282853
• p-INVERT of the positive integers, where p(S) = 1 - 6*S + S^2.at n=4A291028
• a(n) is the prime index of A191304(n+1).at n=15A291153
• a(0) = 1; a(n) = Sum_{k=0..floor(n/4)} binomial(n+1,4*k+1) * a(k).at n=14A352902
• Theta series of 15-dimensional lattice Kappa_15.at n=3A362875
• Triangle read by rows: T(n, k) = [x^k] (n*x + 1)*Hypergeometric([-n, -n + 1], [1], x).at n=52A371401