335790

Appears in sequences

• Tritriangular numbers: a(n) = binomial(binomial(n,2),2) = n*(n+1)*(n-1)*(n-2)/8.at n=41A050534
• Consider 2n tennis players; a(n) is the number of matches needed to let every possible pair play each other.at n=19A062346
• Triangular numbers with square pyramidal indices.at n=13A076767
• Triangular numbers that are sandwiched between two semiprimes; or triangular numbers t such that t-1 and t+1 are both semiprime.at n=31A121898
• Triangular array read by rows. T(n,k) is the number of partial functions on [n] with index k, n=0 implies k=1, otherwise n >= 1, 1 <= k <= n.at n=25A341093
• Triangular numbers that are sandwiched between two squarefree semiprimes.at n=29A375384