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A133568 Triangle: row n is least sequence of n positive integers such that A131655(n) distinct rational numbers are generated only from them using only +, -, * and / and each number in the row no more than once in a given expression. 1
1, 2, 3, 2, 5, 22 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

As in A131655, these operations are all considered to be the usual binary operations only; in particular, -x is not a permitted expression.

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

Row 3: 2, 5, 22 generates these A131655(3)=89 distinct rational numbers:

-108, -100, -66, -39, -34, -25, -108/5, -20, -39/2, -19, -17, -15, -12,

-17/2, -22/3, -6, -54/11, -4, -3, -12/5, -39/22, -1/4, -3/22, -2/17, 1/55,

2/27, 1/11, 5/44, 2/17, 3/22, 5/24, 5/22, 1/4, 7/22, 2/5, 5/11,

39/22, 2, 11/5, 49/22, 12/5, 5/2, 3, 22/7, 4, 22/5, 24/5, 54/11, 5,

56/11, 6, 32/5, 7, 22/3, 17/2, 44/5, 10, 11, 12, 27/2, 15, 16, 17, 19,

39/2, 20, 108/5, 22, 112/5, 24, 49/2, 25, 27, 29, 32, 34, 39, 44, 49,

54, 55, 66, 100, 108, 110, 112, 120, 154, 220.

No smaller sequence of three positive integers generates this many distinct results.

CROSSREFS

Cf. A131655.

Sequence in context: A162687 A010242 A086507 * A120716 A084318 A084317

Adjacent sequences:  A133565 A133566 A133567 * A133569 A133570 A133571

KEYWORD

more,nonn,tabl,hard

AUTHOR

Rick L. Shepherd, Sep 16 2007

STATUS

approved

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Last modified February 23 23:56 EST 2018. Contains 299595 sequences. (Running on oeis4.)