157080

Appears in sequences

• a(n) = floor(n*(n-1)*(n-2)*(n-3)/9).at n=36A011919
• Number of diagonal dissections of an n-gon into 5 regions.at n=8A033277
• Theta series of 20-dimensional lattice L_20 with group 2.M_22.2.at n=6A033288
• Triangle inverse to that in A046899.at n=50A046900
• Partial sums of A051878.at n=13A050404
• Tritriangular numbers: a(n) = binomial(binomial(n,2),2) = n*(n+1)*(n-1)*(n-2)/8.at n=34A050534
• Numbers k such that phi(k) < k/5.at n=19A066765
• Integers x such that for some integer y we have uphi(x) = uphi(y) = x-y, where uphi(n) = A047994(n) is the unitary totient function: If n = Product p_i^e_i, uphi(n) = Product (p_i^e_i - 1).at n=17A067739
• Integers which have more than one coprime factorization into nonprime powers which sum to the same number.at n=18A072940
• Triangular numbers which are 8-almost primes.at n=16A076582
• Highly composite triangular numbers: triangular numbers where the number of divisors increases to a record.at n=14A076711
• Smallest triangular number divisible by exactly n triangular numbers.at n=19A076983
• a(1) = 1; for n > 1, a(n) = smallest triangular number which is n times another triangular number > 1, or -1 if no such number exists.at n=43A077672
• Least common multiple of {d-1: d > 1 and d divides n}.at n=35A084190
• a(n) = A084190(A084190(n)).at n=9A084191
• Triangular numbers that set a new record for number of triangular divisors.at n=12A084260
• Numbers that can be expressed as the difference of the squares of primes in exactly twelve distinct ways.at n=3A092008
• n-th partial product of A093839.at n=6A093842
• Triangle read by rows: T(n, k) = binomial(2*n, k-1)*binomial(2*n-k-1, n-k)/n for n, k >= 1, and T(n, 0) = 0^n.at n=51A094385
• a(n) = (n+1)*(n+2)^2*(n+3)*(n+4)*(3*n+5)/240.at n=13A114243