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A227639 Number of nX4 0,1 arrays indicating 2X2 subblocks of some larger (n+1)X5 binary array having determinant equal to one, with rows and columns of the latter in nondecreasing lexicographic order 1
4, 23, 127, 667, 3202, 13740, 53575, 192191, 640831, 2002960, 5909556, 16555375, 44257697, 113385871, 279415526, 664438386, 1528929898, 3412860357, 7406164606, 15655003700, 32288642035, 65081639197, 128377414029, 248137470904 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 4 of A227641

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = (1/2534272925184000)*n^19 - (1/36377123328000)*n^18 + (67/29640619008000)*n^17 - (23/219469824000)*n^16 + (19/4245696000)*n^15 - (1120937/7846046208000)*n^14 + (30866519/7846046208000)*n^13 - (315413129/3621252096000)*n^12 + (325169513/201180672000)*n^11 - (668686973/27433728000)*n^10 + (17219161039/57480192000)*n^9 - (639427718879/219469824000)*n^8 + (85152990271801/3923023104000)*n^7 - (121633558587211/1069915392000)*n^6 + (4714045506851/14859936000)*n^5 + (29982367841021/50295168000)*n^4 - (119301334227941/11027016000)*n^3 + (805259895738317/15437822400)*n^2 - (4914764430377/38798760)*n + 130960 for n>9

EXAMPLE

Some solutions for n=4

..0..0..1..0....0..0..0..0....0..0..0..1....0..0..0..0....0..0..1..0

..0..1..0..1....0..0..1..1....0..0..1..0....0..0..1..1....0..1..0..0

..0..0..1..0....0..1..0..0....0..0..1..1....1..0..0..1....0..1..0..0

..1..0..0..0....1..0..1..1....1..0..0..0....0..0..0..0....1..0..0..0

CROSSREFS

Sequence in context: A144465 A024050 A236421 * A291026 A239399 A193808

Adjacent sequences:  A227636 A227637 A227638 * A227640 A227641 A227642

KEYWORD

nonn

AUTHOR

R. H. Hardin Jul 18 2013

STATUS

approved

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Last modified June 23 21:56 EDT 2021. Contains 345402 sequences. (Running on oeis4.)