

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.


4



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
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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), 881888.


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.
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



