221445

Appears in sequences

• Tritriangular numbers: a(n) = binomial(binomial(n,2),2) = n*(n+1)*(n-1)*(n-2)/8.at n=37A050534
• Consider 2n tennis players; a(n) is the number of matches needed to let every possible pair play each other.at n=17A062346
• Numbers that are n-gons for three or more n's, where n=3,4,5,...,16.at n=15A062712
• Smallest triangular number which is a multiple (>1) of the n-th triangular number.at n=36A068084
• Numbers n such that 8*n+1 is a cube.at n=15A165220
• Triangular numbers that are the product of three distinct triangular numbers greater than 1.at n=27A225440
• Number of (n+1)X(2+1) 0..2 arrays with no element equal to a strict majority of its horizontal, diagonal and antidiagonal neighbors, with values 0..2 introduced in row major order.at n=3A231414
• T(n,k)=Number of (n+1)X(k+1) 0..2 arrays with no element equal to a strict majority of its horizontal, diagonal and antidiagonal neighbors, with values 0..2 introduced in row major order.at n=13A231419
• Number of (4+1)X(n+1) 0..2 arrays with no element equal to a strict majority of its horizontal, diagonal and antidiagonal neighbors, with values 0..2 introduced in row major order.at n=1A231423
• Triangular numbers composed of only digits with line segments or both line segments and curves {1, 2, 4, 5, 7}.at n=30A247021
• Triangular numbers that are repdigits with length > 2 in some base.at n=38A274084
• 32*a(n) is the denominator of the squared circumradius of a cyclic quadrilateral with sides n, n+1, n+2, n+3.at n=34A351697