174924

Appears in sequences

• a(n) = (1/2) * Sum_{k=1..n} (n+k)!/(k!)^2.at n=6A073013
• a(n) = number of subsets S of {1,2,...,n} having more than 1 element such that (difference between least two elements of S) = difference between greatest two elements of S.at n=19A357282