A228219 Number of second differences of arrays of length 4 of numbers in 0..n.

15, 49, 103, 177, 271, 385, 519, 673, 847, 1041, 1255, 1489, 1743, 2017, 2311, 2625, 2959, 3313, 3687, 4081, 4495, 4929, 5383, 5857, 6351, 6865, 7399, 7953, 8527, 9121, 9735, 10369, 11023, 11697, 12391, 13105, 13839, 14593, 15367, 16161, 16975, 17809

Offset: 1

Author

R. H. Hardin, Aug 16 2013

Keywords

• nonn

Comments

Row 2 of A228218.

Examples

			Some solutions for n=4:
..1....1....1....5....6....1....2...-5....8....4...-5....8....1....5...-7....0
..4....2...-3....1...-6....1....1...-1...-7....1....0...-4....5...-7....6....6
		

Links

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

Crossrefs

Cf. A228218, A272039.

Formula

Empirical: a(n) = 10*n^2 + 4*n + 1 = A272039(n).

Conjectures from Colin Barker, Mar 16 2018: (Start)

G.f.: x*(15 + 4*x + x^2) / (1 - x)^3.

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>3.

(End)