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A037291 Number of rings with 1 containing n elements. 7
1, 1, 1, 4, 1, 1, 1, 11, 4, 1, 1, 4, 1, 1, 1, 50, 1, 4, 1, 4, 1, 1, 1, 11, 4, 1, 12, 4, 1, 1, 1, 208, 1, 1, 1, 16, 1, 1, 1, 11, 1, 1, 1, 4, 4, 1, 1, 50, 4, 4, 1, 4, 1, 11, 1, 11, 1, 1, 1, 4, 1, 1, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Many authors simply call these "rings". They are also known as unital rings, rings with unity, or rings with identity. - Charles R Greathouse IV, Aug 12 2015

LINKS

Table of n, a(n) for n=1..63.

C. Noebauer, Home page [Archived copy as of 2008 from web.archive.org]

CROSSREFS

Cf. A027623, A037221.

Sequence in context: A184729 A127707 A113196 * A222317 A063851 A124777

Adjacent sequences:  A037288 A037289 A037290 * A037292 A037293 A037294

KEYWORD

nonn,nice,hard

AUTHOR

Christian G. Bower, Jun 15 1998.

EXTENSIONS

a(16) and a(32)-a(63) from Christof Noebauer (christof.noebauer(AT)algebra.uni-linz.ac.at), Sep 29, 2000

STATUS

approved

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Last modified December 8 09:03 EST 2016. Contains 278906 sequences.