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A127707 Number of commutative rings with 1 containing n elements. 12
1, 1, 1, 4, 1, 1, 1, 10, 4, 1, 1, 4, 1, 1, 1, 37, 1, 4, 1, 4, 1, 1, 1, 10, 4, 1, 11, 4, 1, 1, 1, 109, 1, 1, 1, 16, 1, 1, 1, 10, 1, 1, 1, 4, 4, 1, 1, 37, 4, 4, 1, 4, 1, 11, 1, 10, 1, 1, 1, 4, 1, 1, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
Is this a multiplicative function?
Answer: yes! See the Eric M. Rains link for a proof for the result for all unital rings; restricting to commutative rings does not affect the essence of the proof. - Jianing Song, Feb 02 2020
LINKS
C. Noebauer, Home page and Table of numbers of small rings [Archived copies from web.archive.org]
FORMULA
a(n) = A037291(n) - A127708(n). - Bernard Schott, Apr 19 2022
CROSSREFS
Sequence in context: A303278 A222639 A184729 * A113196 A037291 A222317
KEYWORD
more,nice,nonn,mult
AUTHOR
Hugues Randriam (randriam(AT)enst.fr), Jan 24 2007
EXTENSIONS
Keyword 'mult' added by Jianing Song, Feb 02 2020
a(32)-a(63) using Nöbauer's data added by Andrey Zabolotskiy, Apr 18 2022
a(32) = 109 corrected by Bernard Schott, Apr 19 2022
STATUS
approved

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Last modified February 27 09:53 EST 2024. Contains 370377 sequences. (Running on oeis4.)