A172993 Maximal number of 4-tree rows in n-tree orchard problem in which the coordinates of trees may be complex numbers.

0, 0, 0, 1, 1, 1, 2, 2, 3, 5, 6, 9, 9, 11, 13, 15, 17, 18, 20, 23

Offset

1,7

Links

Table of n, a(n) for n=1..20.

Zhao Hui Du, Orchard planting problem with 4 trees per row

Example

a(12)=9: Such as 12 trees in 9 rows: example for 12 trees with 9 rows: ABCD,AEFG,AHIJ,BEHK,BFIL,CEJL,CGIK,DFJK,DGHL. Let t^2+t+1=0, coordinate in projective plane: A[0:1:0], B[1:0:0], C[1:1+t:0], D[1:t:0], E(0,0), F(0,1), G(0,-t), H(1,0), I(1,1), J(1,t+1), K(1+t,0), L(-t,1).

Crossrefs

Cf. A006065.

Sequence in context: A326548 A326687 A352524 * A335755 A325338 A143438

Adjacent sequences: A172990 A172991 A172992 * A172994 A172995 A172996

Keyword

hard,more,nonn

Author

Zhao Hui Du, Feb 07 2010

Extensions

a(12) corrected by Zhao Hui Du, Oct 30 2019

Status

approved