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 A086265 Numerators of mean number of s-clusters in an n X n (0,1)-matrix. 1
 1, 17, 897, 168529, 118183389 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Eric Weisstein's World of Mathematics, s-Cluster EXAMPLE 1/2, 17/16, 897/512, 168529/65536, 118183389/33554432... MATHEMATICA For[n = 1, n <= 5, n++, cnt = 0; For[ii = 0, ii <= 2^(n^2), ii++,   A = Partition[IntegerDigits[ii, 2, n^2], n];   G = EmptyGraph[n^2];   deleteG = 0;   vert = {0, -1};   horiz = {-1, 0};   For[i = 1, i <= n, i++,    For[j = 1, j <= n, j++,     If[A[[i, j]] == 1,      For[k = 1, k <= 2, k++,       If[A[[i + vert[[k]], j + horiz[[k]]]] == 1,        G = AddEdge[G, {j + (i - 1) n, j + horiz[[k]] + (i - 1) n + n vert[[k]]}];        ]       ],      deleteG++;      ]     ]    ];   CC = ConnectedComponents[G];   cnt += (Length[CC] - deleteG);   ]; Print[cnt] ] (* Luca Petrone, May 09 2018 *) CROSSREFS Cf. A002416. Sequence in context: A221324 A124235 A218660 * A156138 A229261 A196873 Adjacent sequences:  A086262 A086263 A086264 * A086266 A086267 A086268 KEYWORD nonn,frac,more AUTHOR Eric W. Weisstein, Jul 14 2003 EXTENSIONS a(5) from Luca Petrone, May 09 2018 STATUS approved

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Last modified June 18 01:16 EDT 2021. Contains 345098 sequences. (Running on oeis4.)