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A203928 Number of (n+1) X 3 0..5 arrays with every 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements. 1
4356, 106596, 2543436, 60873876, 1456391916, 34845401556, 833700866796, 19946896311636, 477243883220076, 11418404289436116, 273193561903563756, 6536353100235366996, 156386964438192169836, 3741670970218511256276 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A203934.

LINKS

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

FORMULA

Empirical: a(n) = 21*a(n-1) + 70*a(n-2).

Empirical g.f.: 36*x*(121 + 420*x) / (1 - 21*x - 70*x^2). - Colin Barker, Jun 05 2018

EXAMPLE

Some solutions for n=4:

..3..3..5....5..4..0....1..4..4....3..0..5....5..3..5....2..0..5....1..1..5

..0..3..3....2..5..4....1..1..4....4..3..0....5..5..1....5..2..0....4..1..1

..4..0..3....5..4..1....1..5..1....2..4..3....5..1..5....0..5..2....1..4..1

..4..4..0....0..5..4....0..1..3....3..2..4....1..5..4....5..3..5....0..1..2

..3..4..4....3..0..5....2..0..1....5..3..2....3..1..5....5..5..5....5..0..1

CROSSREFS

Cf. A203934.

Sequence in context: A250817 A154084 A285040 * A340457 A176111 A164517

Adjacent sequences:  A203925 A203926 A203927 * A203929 A203930 A203931

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 08 2012

STATUS

approved

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Last modified June 28 19:10 EDT 2022. Contains 354907 sequences. (Running on oeis4.)