A272081 Irregular triangle read by rows: strictly decreasing positive integer sequences in lexicographic order with the property that the sum of inverses is the inverse of an integer.

1, 2, 3, 4, 5, 6, 6, 3, 6, 3, 2, 7, 8, 9, 10, 11, 12, 12, 4, 12, 6, 12, 6, 4, 12, 6, 4, 2, 13, 14, 15, 15, 10, 15, 10, 3, 15, 10, 3, 2, 15, 10, 6, 15, 12, 10, 15, 12, 10, 4, 15, 12, 10, 4, 2, 15, 12, 10, 6, 4, 3, 16, 17, 18, 18, 9, 18, 9, 3, 18, 9, 3, 2, 18, 9

Offset: 1

Author

Peter Kagey, Apr 19 2016

Keywords

• nonn
• tabf

Examples

			First 18 rows:
  [1]           because 1 is self-inverse.
  [2]           because 1/2 is the inverse of an integer.
  [3]
  [4]           (...)
  [5]
  [6]
  [6, 3]        because 1/6 + 1/3              = 1/2.
  [6, 3, 2]     because 1/6 + 1/3 + 1/2        = 1/1.
  [7]
  [8]
  [9]           (...)
  [10]
  [11]
  [12]
  [12, 4]       because 1/12 + 1/4             = 1/3.
  [12, 6]       because 1/12 + 1/6             = 1/4.
  [12, 6, 4]    because 1/12 + 1/6 + 1/4       = 1/2.
  [12, 6, 4, 2] because 1/12 + 1/6 + 1/4 + 1/2 = 1/1.
		

Links

• Peter Kagey, Table of n, a(n) for n = 1..2170 (All rows with first term less than or equal to 30.)

Crossrefs

Cf. A272020, A272034, A272082, A272083.