# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a174564 Showing 1-1 of 1 %I A174564 #5 Dec 18 2015 18:17:24 %S A174564 0,1,13,522,27828,1867363 %N A174564 Let J_n be n X n matrix which contains 1's only, I=I_n be the n X n identity matrix and P=P_n be the incidence matrix of the cycle (2,3,...,n,1). Then a(n) is the number of (0,1) n X n matrices A<=J_n-I-P with exactly two 1's in every row and column %D A174564 V. S. Shevelev, Development of the rook technique for calculating the cyclic indicators of (0,1)-matrices, Izvestia Vuzov of the North-Caucasus region, Nature sciences 4 (1996), 21-28 (in Russian). %D A174564 S. E. Grigorchuk, V. S. Shevelev, An algorithm of computing the cyclic indicator of couples discordant permutations with restricted position, Izvestia Vuzov of the North-Caucasus region, Nature sciences 3 (1997), 5-13 (in Russian). %Y A174564 Cf. A001499 A007107 A082491 A000186 %K A174564 nonn,uned %O A174564 3,3 %A A174564 _Vladimir Shevelev_, Mar 22 2010 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE