This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A185178 #41 Jul 24 2025 04:00:55 %S A185178 1,1,2,4,8,18,32,61,109 %N A185178 Number of distinct values of the permanent of an n X n (0,1)-matrix with exactly three 1's in each row and each column. %C A185178 The values a(n) are unknown for n>=9. %C A185178 a(12) >= 170, a(13) >= 276, a(14) >= 438, a(15) >= 547. - _Robert P. P. McKone_, Jul 14 2025 %D A185178 V. I. Bolshakov, On spectrum of permanent on Lambda_n^k, Proc. of Seminar on Discrete Math. and Appl., Moscow State Univ. (1986), 65-73 (in Russian). %H A185178 Robert P. P. McKone, <a href="/A185178/a185178.txt">One example matrix for each known permanent for a(3)..a(15), with a(11)..a(15) being incomplete</a> %H A185178 Robert P. P. McKone, <a href="/A185178/a185178_1.txt">Complete frequence counts for each permanent for a(3)..a(11)</a> %H A185178 Robert P. P. McKone, <a href="/A185178/a185178.cpp.txt">Robert P. P. McKone, C++ code for enumerating and counting each permanent's frequency for a(n)</a> %H A185178 V. S. Shevelev, <a href="http://dx.doi.org/10.1007/BF01104103">Some problems of the theory of enumerating the permutations with restricted position</a>, Journal of Soviet Mathematics, 61 (4) (1992) 2272-2317 (see pp. 2307-2309). %Y A185178 Cf. A185179 (values of the permanent), A176211, A176212. %Y A185178 Cf. A001501 (number of n X n (0,1)-matrix with exactly three 1's in each row and each column). %K A185178 nonn,hard,more %O A185178 3,3 %A A185178 _Vladimir Shevelev_, Feb 19 2011 %E A185178 a(9)-a(11) from _Robert P. P. McKone_, Jul 22 2025