“231 (number)”的意思、由来-开放百科全书

词条

231 (number)

释义

In mathematics
In chemistry
In other fields
References

231 (two hundred [and] thirty-one) is the natural number following 230 and preceding 232.

In mathematics

Two hundred [and] thirty-one 231 = 3·7·11, sphenic number, triangular number, hexagonal number, octahedral number,^[1] centered octahedral number,^[2] the number of integer partitions of 16, Mertens function returns 0,^[3] and is the number of cubic inches in a U.S. liquid gallon.

In chemistry

Ac-231 is an isotope of actinium.
Am-231 is an artificial isotope of americium.
Pa-231 is a naturally occurring isotope of protactinium.
Ra-231 is an isotope of radium.
Th-231 is an isotope of thorium.

In other fields

231 is:

The year A.D. 231 or 231 BC.
+231 is the country code for Liberia.
Pacific 231, an orchestral work by French composer Arthur Honegger.
Pacific 231, a 1949 short film directed by Jean Mitry.
M-231 (Michigan highway), a highway in Michigan

References

1. ^{{Cite web|url=https://oeis.org/A005900|title=Sloane's A005900 : Octahedral numbers|last=|first=|date=|website=The On-Line Encyclopedia of Integer Sequences|publisher=OEIS Foundation|access-date=2016-05-24}}
2. ^{{Cite web|url=https://oeis.org/A001845|title=Sloane's A001845 : Centered octahedral numbers|last=|first=|date=|website=The On-Line Encyclopedia of Integer Sequences|publisher=OEIS Foundation|access-date=2016-05-24}}
3. ^{{Cite web|url=https://oeis.org/A028442|title=Sloane's A028442 : Numbers n such that Mertens' function is zero|last=|first=|date=|website=The On-Line Encyclopedia of Integer Sequences|publisher=OEIS Foundation|access-date=2016-05-24}}

1 : Integers

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