

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
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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 selfinverse.
[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



