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A248434 Number of length 1+2 0..n arrays with every three consecutive terms having the sum of some two elements equal to twice the third 2
2, 9, 16, 29, 42, 61, 80, 105, 130, 161, 192, 229, 266, 309, 352, 401, 450, 505, 560, 621, 682, 749, 816, 889, 962, 1041, 1120, 1205, 1290, 1381, 1472, 1569, 1666, 1769, 1872, 1981, 2090, 2205, 2320, 2441, 2562, 2689, 2816, 2949, 3082, 3221, 3360, 3505, 3650 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 1 of A248433

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) -2*a(n-3) +a(n-4)

Empirical for n mod 2 = 0: a(n) = (3/2)*n^2 + n + 1

Empirical for n mod 2 = 1: a(n) = (3/2)*n^2 + n - (1/2)

EXAMPLE

Some solutions for n=6

..2....3....6....1....3....4....3....1....6....2....4....0....4....5....4....3

..6....1....2....0....2....3....3....2....5....3....0....1....3....6....4....5

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

CROSSREFS

Sequence in context: A003325 A101420 A275498 * A275395 A213389 A237282

Adjacent sequences:  A248431 A248432 A248433 * A248435 A248436 A248437

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 06 2014

STATUS

approved

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Last modified October 20 05:42 EDT 2017. Contains 293601 sequences.