%I #37 Feb 02 2023 15:29:09
%S 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,
%T 208,1,1,1,16,1,1,1,11,1,1,1,4,4,1,1,50,4,4,1,4,1,12,1,11,1,1,1,4,1,1,
%U 4
%N Number of rings with 1 containing n elements.
%C 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
%C 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
%H GĂ©rard P. Michon, <a href="https://www.numericana.com/answer/rings.htm">Ring Theory</a>, Numericana, 2000-2022.
%H C. Noebauer, <a href="https://web.archive.org/web/20080111141811/http://www.algebra.uni-linz.ac.at/~noebsi/">Home page</a> and <a href="https://web.archive.org/web/20061002201537/http://www.algebra.uni-linz.ac.at/~noebsi/ringtable.html">Table of numbers of small rings</a> [Archived copies]
%H Eric M. Rains, <a href="/A037291/a037291.txt">The number of unital rings with n elements is a multiplicative function of n</a>.
%Y Cf. A027623, A037221, A127707.
%K nonn,nice,hard,mult
%O 1,4
%A _Christian G. Bower_, Jun 15 1998
%E a(16) and a(32)-a(63) from Christof Noebauer (christof.noebauer(AT)algebra.uni-linz.ac.at), Sep 29 2000
%E Keyword 'mult' added by _Jianing Song_, Feb 02 2020
%E a(54) corrected by _Andrey Zabolotskiy_, Feb 02 2023