39780

Appears in sequences

• Number of triangles a queen can make (starting anywhere) on an n X n board.at n=27A030117
• a(n) = A045820(n)/2.at n=21A045822
• Integers k such that omega(k) = omega(k-1) + omega(k-2) + omega(k-3), where omega(n) is the number of distinct prime factors of n.at n=33A076252
• Expansion of Hypergeometric function F(1/12, 5/12; 1; 1728*x) in powers of x.at n=2A092870
• Numbers in the cycle-attractors of length=14 of the function f(x)=A063919(x).at n=25A097030
• Triangle read by rows: T(n,k) is the number of hill-free Schroeder paths of length 2n that have k weak ascents (1<=k<=n-1 for n>=2; k=1 for n=1). A Schroeder path of length 2n is a lattice path from (0,0) to (2n,0) consisting of U=(1,1), D=(1,-1) and H=(2,0) steps and never going below the x-axis. A hill is a peak at height 1. A weak ascent in a Schroeder path is a maximal sequence of consecutive U and H steps.at n=32A114691
• Numbers k such that if you subtract k-reversed from k you get a natural number with the same digits as k.at n=12A121969
• Record differences for n^2 - phi(n)*sigma(n).at n=36A164876
• Numbers with prime factorization pqrs^2t^2.at n=17A189989
• Equals two maps: number of nX4 binary arrays indicating the locations of corresponding elements equal to exactly two of their horizontal and vertical neighbors in a random 0..2 nX4 array.at n=3A220374
• T(n,k)=Equals two maps: number of nXk binary arrays indicating the locations of corresponding elements equal to exactly two of their horizontal and vertical neighbors in a random 0..2 nXk array.at n=24A220375
• Number of (n+1)X3 0..3 arrays with every row and column least squares fitting to a positive slope straight line.at n=2A222926
• Number of (n+1)X4 0..3 arrays with every row and column least squares fitting to a positive slope straight line.at n=1A222927
• T(n,k)=Number of (n+1)X(k+1) 0..3 arrays with every row and column least squares fitting to a positive slope straight line.at n=7A222929
• T(n,k)=Number of (n+1)X(k+1) 0..3 arrays with every row and column least squares fitting to a positive slope straight line.at n=8A222929
• a(n) = n*(n+1)*(13*n+2)/6.at n=26A257093
• Magic sums of 4 X 4 magic squares composed of odd squares.at n=16A271582
• Positive integers that have a record number of divisors in Gaussian integers.at n=36A279254
• Numbers x such that x = Sum_{i=1..k} (x mod d_(x-i)) + Sum_{i=1..k} (x mod d_(x+i)) for some k, where d_(x-i) and d_(x+i) are the aliquot parts of (x-i) and (x+i).at n=13A286873
• Numbers that are members of unitary sigma aliquot cycles (union of unitary perfect, unitary amicable and unitary sociable numbers).at n=43A327157