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A228220 Number of second differences of arrays of length 5 of numbers in 0..n. 1
31, 199, 625, 1429, 2731, 4651, 7309, 10825, 15319, 20911, 27721, 35869, 45475, 56659, 69541, 84241, 100879, 119575, 140449, 163621, 189211, 217339, 248125, 281689, 318151, 357631, 400249, 446125, 495379, 548131, 604501, 664609, 728575 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 20*n^3 + 9*n^2 + 1*n + 1.
Conjectures from Colin Barker, Sep 10 2018: (Start)
G.f.: x*(31 + 75*x + 15*x^2 - x^3) / (1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4.
(End)
EXAMPLE
Some solutions for n=4:
.-2....1...-5....4....0....1....1....3...-2....4...-5...-8....4...-4....0....3
.-2...-2....6....0....2...-3....4....0....5....3....7....7...-6...-4....1...-7
.-2....5....0...-2...-5....7...-7...-2...-3...-6...-2...-2....3....4...-3....4
CROSSREFS
Row 3 of A228218.
Sequence in context: A139998 A142654 A137657 * A125341 A126499 A297758
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 16 2013
STATUS
approved

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Last modified March 1 06:29 EST 2024. Contains 370430 sequences. (Running on oeis4.)