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A182173 Number of inequivalent expressions involving n operands. 1
2, 10, 94, 1466, 31814, 887650, 30259198, 1218864842, 56644903958, 2983300619410, 175598066553166, 11423394497044154, 813897286250604326, 63030237104398839490, 5271647928235911880222, 473558482553909252128298, 45473767604938843870986422, 4648336478135316689480390770 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Each operand must be used exactly once, and the only allowed operations are addition, subtraction, multiplication, division, and unary minus. Parentheses are permitted. This sequence differs from A140606 by allowing unary minus.

LINKS

David Radcliffe, Table of n, a(n) for n = 1..90

David Radcliffe, Python script

Wikipedia, 24 Game

EXAMPLE

When n=2, there are 10 inequivalent expressions: a+b, a-b, b-a, -a-b, a*b, -a*b, a/b, -a/b, b/a, -b/a.

CROSSREFS

Cf. A140606.

Sequence in context: A231375 A100622 A103436 * A160940 A193290 A193435

Adjacent sequences:  A182170 A182171 A182172 * A182174 A182175 A182176

KEYWORD

nonn

AUTHOR

David Radcliffe, Apr 16 2012

STATUS

approved

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Last modified February 25 11:05 EST 2018. Contains 299653 sequences. (Running on oeis4.)