A280518 Number of increasing sequences of n positive integers with reciprocals adding up to an integer.

1, 0, 1, 7, 78, 2392, 248085, 151428144

Offset

1,4

Links

Table of n, a(n) for n=1..8.

Example

a(4)=7 enumerates sequences: (1,2,3,6), (2,4,5,20), (2,4,6,12), (2,3,7,42), (2,3,8,24), (2,3,9,18), and (2,3,10,15).

Crossrefs

Row sums of A280520.

Cf. A006585 (adding up to 1), A156871 (nondecreasing sequences), A280517 (ordered sequences).

Sequence in context: A186657 A079590 A202755 * A156714 A350964 A106110

Adjacent sequences: A280515 A280516 A280517 * A280519 A280520 A280521

Keyword

nonn,hard,more

Author

Max Alekseyev, Jan 04 2017

Status

approved