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A272083 Irregular triangle read by rows: strictly decreasing positive integer sequences in lexicographic order with the property that the sum of inverses equals one. 7
1, 6, 3, 2, 12, 6, 4, 2, 15, 10, 3, 2, 15, 12, 10, 4, 2, 15, 12, 10, 6, 4, 3, 18, 9, 3, 2, 18, 12, 9, 4, 2, 18, 12, 9, 6, 4, 3, 18, 15, 10, 9, 6, 2, 18, 15, 12, 10, 9, 4, 3, 20, 5, 4, 2, 20, 6, 5, 4, 3, 20, 12, 6, 5, 2, 20, 15, 10, 5, 4, 3, 20, 15, 12, 10, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Peter Kagey, Table of n, a(n) for n = 1..1578 (All rows with first term less than or equal to 30.)

Wikipedia, Erdős-Graham problem.

EXAMPLE

First six rows:

[1]                   because 1/1 = 1.

[6, 3, 2]             because 1/6 + 1/3 + 1/2 = 1.

[12, 6, 4, 2]         because 1/12 + 1/6 + 1/4 + 1/2 = 1.

[15, 10, 3, 2]        because 1/15 + 1/10 + 1/3 + 1/2 = 1.

[15, 12, 10, 4, 2]    because 1/15 + 1/12 + 1/10 + 1/4 + 1/2 = 1.

[15, 12, 10, 6, 4, 3] because 1/15 + 1/12 + 1/10 + 1/6 + 1/4 + 1/3 = 1.

CROSSREFS

Cf. A073546, A216975, A216993, A272020, A272036, A272081, A272082.

Sequence in context: A021162 A114348 A280680 * A096840 A096685 A307150

Adjacent sequences:  A272080 A272081 A272082 * A272084 A272085 A272086

KEYWORD

nonn,tabf

AUTHOR

Peter Kagey, Apr 19 2016

STATUS

approved

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Last modified August 3 22:03 EDT 2021. Contains 346441 sequences. (Running on oeis4.)