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 A037291 Number of rings with 1 containing n elements. 9
 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 Is this sequence multiplicative? That is, if p and q are distinct primes, is it true that a(p^i*q^j) = a(p^i)*a(q^j)? - Jianing Song, Oct 26 2019. The answer is yes - see the Eric M. Rains link. - N. J. A. Sloane, Oct 27 2019 LINKS 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,mult 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 Keyword 'mult' added by Jianing Song, Feb 02 2020 STATUS approved

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Last modified September 22 06:08 EDT 2020. Contains 337289 sequences. (Running on oeis4.)