A379452 Number of compositions (ordered partitions) of 1 into n distinct reciprocals of positive integers.

1, 0, 6, 144, 8640, 1670400, 1238655600, 6095673521280

Offset: 1

Author

Ilya Gutkovskiy, Dec 23 2024

Keywords

• nonn
• hard
• more

Examples

			a(3) = 6 because we have 1 = 1/2 + 1/3 + 1/6
                           = 1/2 + 1/6 + 1/3
                           = 1/3 + 1/2 + 1/6
                           = 1/3 + 1/6 + 1/2
                           = 1/6 + 1/2 + 1/3
                           = 1/6 + 1/3 + 1/2.
		

Crossrefs

Cf. A002966, A002967, A006585.

Formula

a(n) = n! * A006585(n).