56979

Appears in sequences

• Numbers k with property that there is an m = m(k) such that m(m+1)/2 divides k(k+1)/2 and m(k) > m(i) for all i < k.at n=26A309423
• a(n) is the number of edges formed by n-secting the angles of a nonagon (enneagon).at n=40A335783
• Indices of triangular numbers that are ten times other triangular numbers.at n=9A341895