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 A227086 Number of n X 3 binary arrays indicating whether each 2 X 2 subblock of a larger binary array has lexicographically increasing rows and columns, for some larger (n+1) X 4 binary array with rows and columns of the latter in lexicographically nondecreasing order. 1
 7, 29, 99, 302, 842, 2177, 5281, 12128, 26548, 55684, 112389, 219051, 413531, 758154, 1353017, 2355283, 4006629, 6671623, 10890535, 17450956, 27483624, 42589055, 65002969, 97810106, 145217866, 212903302, 308449369, 441889009, 626378657 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = (1/39916800)*n^11 + (1/3628800)*n^10 + (1/120960)*n^9 + (1/8640)*n^8 + (1481/1209600)*n^7 + (1153/172800)*n^6 + (14807/181440)*n^5 + (92843/362880)*n^4 + (10901/16800)*n^3 + (19709/7200)*n^2 + (20959/9240)*n + 1. Conjectures from Colin Barker, Sep 07 2018: (Start) G.f.: x*(7 - 55*x + 213*x^2 - 512*x^3 + 837*x^4 - 964*x^5 + 794*x^6 - 468*x^7 + 197*x^8 - 58*x^9 + 11*x^10 - x^11) / (1 - x)^12. a(n) = 12*a(n-1) - 66*a(n-2) + 220*a(n-3) - 495*a(n-4) + 792*a(n-5) - 924*a(n-6) + 792*a(n-7) - 495*a(n-8) + 220*a(n-9) - 66*a(n-10) + 12*a(n-11) - a(n-12) for n>12. (End) EXAMPLE Some solutions for n=4: ..1..0..0....1..1..0....0..1..0....0..0..0....0..0..0....0..1..0....0..0..1 ..0..0..0....1..0..0....1..1..0....0..0..0....0..1..0....1..1..0....0..1..1 ..0..0..0....0..0..1....1..0..1....0..0..0....0..1..0....1..0..0....0..0..0 ..0..0..0....0..0..1....0..1..1....0..0..0....0..0..0....0..0..1....1..1..0 CROSSREFS Column 3 of A227089. Sequence in context: A042609 A002941 A193655 * A102485 A246038 A049349 Adjacent sequences:  A227083 A227084 A227085 * A227087 A227088 A227089 KEYWORD nonn AUTHOR R. H. Hardin, Jun 30 2013 STATUS approved

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Last modified January 19 03:54 EST 2020. Contains 331031 sequences. (Running on oeis4.)