77980

Appears in sequences

• Structured truncated tetrahedral numbers.at n=34A100156
• Decagonal numbers divisible by 10.at n=28A117797
• T(n,k) is the number of size k ordered submultisets of the regular multiset {1_1,1_2,...,1_(n-1),1_n, ... ,i_1,i_2,...,i_(n-1),i_n, ... ,n_1,n_2,...,n_(n-1),n_n} (which contains n copies of i for 1 <= i <= n).at n=42A234574
• Numbers k such that k^2 + 1 = p*q, p < q primes and q-p is a power of 2.at n=5A238947
• Expansion of a q-series used by Ramanujan in his Lost Notebook.at n=38A279715