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A014235
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Number of n X n matrices with entries 0 and 1 and no 2 X 2 submatrix of form [ 1 1; 1 0 ].
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2
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1, 2, 12, 128, 2100, 48032, 1444212, 54763088, 2540607060, 140893490432, 9170099291892, 690117597121328, 59318536757456340, 5763381455631211232, 627402010180980401652, 75942075645205885599248
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| sci.math articles 32F8AC4B.90F(AT)cs.tamu.edu (Wenyi - Feng w0f0950(AT)cs.tamu.edu), 5dbci9$85u$1(AT)nntp.ucs.ubc.ca (Robert Israel israel(AT)math.ubc.ca).
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LINKS
| Hyeong-Kwan Ju, Seunghyun Seo, Enumeration of 0/1-matrices avoiding some 2x2 matrices, arXiv:1107.1299.
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FORMULA
| a(n) = sum(k! * stirling2(n+1, k+1)^2, k = 0 .. n);
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MATHEMATICA
| Table[Sum[StirlingS2[n+1, k+1]^2k!, {k, 0, n}], {n, 0, 100}] (* Emanuele Munarini, Jul 04 2011 *)
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PROG
| (Maxima) makelist(sum(stirling2(n+1, k+1)^2*k!, k, 0, n), n, 0, 24); - Emanuele Munarini, Jul 04 2011
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CROSSREFS
| Cf. A023997, A111420.
Sequence in context: A003712 A143136 A097629 * A098628 A123553 A079199
Adjacent sequences: A014232 A014233 A014234 * A014236 A014237 A014238
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KEYWORD
| nonn
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AUTHOR
| Robert Israel (israel(AT)math.ubc.ca)
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EXTENSIONS
| a(0)=1 added by Emanuele Munarini, Jul 04 2011
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