121968

Appears in sequences

• a(n) = (2*n)!^2 / ((n+1)!*n!^3).at n=6A000888
• Expansion of (Product_{j>=1} (1-(-x)^j) - 1)^11 in powers of x.at n=24A047649
• Numbers which in at least two ways are the product of two distinct numbers with the same digits (leading zeros are forbidden).at n=1A077760
• a(1) = 7, a(n) = smallest (nontrivial) multiple of a(n-1) containing n digits, a(n) not equal to 10*a(n-1).at n=5A080451
• a(1) = 8, a(n) = smallest (nontrivial) multiple of a(n-1) containing n digits, a(n) not equal to 10*a(n-1).at n=5A080452
• Duplicate of A000888.at n=6A151392
• Number of 1:4:sqrt(17) proportioned triangles on a (n+1) X (n+1) grid.at n=31A189884
• Table, read by rows, of the number of quivers of affine type A_(n-1) according to the parameter k (n >= 2, 1 <= k <= [n/2]).at n=41A189942
• Numbers with prime factorization pq^2r^2s^4.at n=19A190319
• Irregular triangle read by rows: T(n,k) = number of "pat" permutations of [1..n] with k descents.at n=62A212206
• Number of 2 X 2 matrices with entries in {0,1,...,n} and even trace with no entries repeated.at n=23A280056
• Number of closed meanders with 2n crossings and 5 digons.at n=24A300901
• List of e-perfect numbers that are not e-unitary perfect.at n=2A322858
• The number of grains of sand in the identity element for the 3D sandpile group on an n X n X n cubic grid.at n=31A351379
• a(n) is the smallest number whose divisors include exactly n that can be written in the form m + reverse(m), for some m (A067030).at n=36A358513
• Triangle read by rows: T(n, k) = binomial(2*k, k) * binomial(2*n, n) / (n + 1).at n=27A379100
• Exponential Zumkeller numbers that are not exponential unitary Zumkeller numbers.at n=20A391090