A177862 Irregular triangle read by rows in which row n (n>=0) is a list of the numbers of different regions into which n lines can divide the plane.

1, 2, 3, 4, 4, 6, 7, 5, 8, 9, 10, 11, 6, 10, 12, 13, 14, 15, 16, 7, 12, 15, 16, 17, 18, 19, 20, 21, 22

Offset

0,2

Links

Table of n, a(n) for n=0..28.

O. A. Ivanov, On the number of regions into which n straight lines divide the plane, Amer. Math. Monthly, 117 (2010), 881-888.

Example

Triangle begins:
  1
  2
  3  4
  4  6  7
  5  8  9 10 11
  6 10 12 13 14 15 16
  7 12 15 16 17 18 19 20 21 22
  ...

Crossrefs

A000124, A055503, and A263883 are subsequences.

Cf. A241600.

Sequence in context: A326035 A205787 A072455 * A066981 A130043 A089266

Adjacent sequences: A177859 A177860 A177861 * A177863 A177864 A177865

Keyword

nonn,tabf,more

Author

N. J. A. Sloane, Dec 18 2010

Extensions

Duplicate term 22 removed on row n=6 and example fixed by Luc Rousseau, Feb 25 2019

Status

approved