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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. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

EXAMPLE

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.

CROSSREFS

Cf. A272020, A272034, A272082, A272083.

Sequence in context: A307089 A239132 A307311 * A317582 A293705 A036055

Adjacent sequences:  A272078 A272079 A272080 * A272082 A272083 A272084

KEYWORD

nonn,tabf

AUTHOR

Peter Kagey, Apr 19 2016

STATUS

approved

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Last modified May 28 04:02 EDT 2022. Contains 354112 sequences. (Running on oeis4.)