A082681 Denominator of Sum_{i=n(n-1)/2+1..n(n+1)/2} 1/i.

1, 6, 60, 2520, 20020, 1627920, 124324200, 1694579040, 446626220040, 73706596563600, 35444732266944, 24569517992362200, 3290057629552053360, 551042196782556679200, 71028805196838414285360

Offset: 1

Author

Dean Hickerson, Apr 10 2003

Keywords

• nonn
• frac

Crossrefs

Numerator is in A081971. a(n) is a divisor of A061431(n).

Programs

PARI

a(n) = denominator(sum(i = n*(n-1)/2+1, n*(n+1)/2, 1/i)); \\ Michel Marcus, Aug 29 2013