A190039 Number of nondecreasing arrangements of n+2 numbers in 0..7 with the last equal to 7 and each after the second equal to the sum of one or two of the preceding three.

11, 17, 22, 31, 43, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480, 500, 520, 540, 560, 580, 600, 620, 640, 660, 680, 700, 720, 740, 760, 780, 800, 820, 840, 860, 880, 900, 920, 940, 960, 980, 1000, 1020

Offset

1,1

Comments

Column 7 of A190041.

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = 20*n - 60 for n>5.

Conjectures from Colin Barker, May 04 2018: (Start)

G.f.: x*(11 - 5*x - x^2 + 4*x^3 + 3*x^4 + 5*x^5 + 3*x^6) / (1 - x)^2.

a(n) = 2*a(n-1) - a(n-2) for n>7.

(End)

Example

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

Crossrefs

Cf. A190041.

Sequence in context: A050715 A006618 A184551 * A066074 A106563 A106574

Adjacent sequences: A190036 A190037 A190038 * A190040 A190041 A190042

Keyword

nonn

Author

R. H. Hardin, May 04 2011

Status

approved