

A261595


Triangular array T(n, k) read by rows (n >= 1, 1 <= k <= n): row n gives the lexicographically earliest doubly centrosymmetric characteristic solution to the n queens problem, or n zeros if no doubly centrosymmetric characteristic solution exists. The kth queen is placed in square (k, T(n, k)).


2



1, 0, 0, 0, 0, 0, 2, 4, 1, 3, 2, 5, 3, 1, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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OFFSET

1,7


COMMENTS

See the comments under A260318.


REFERENCES

Maurice Kraitchik: Mathematical Recreations. Mineola, NY: Dover, 2nd ed. 1953, pp. 247255 (The Problem of the Queens).


LINKS

Table of n, a(n) for n=1..66.


EXAMPLE

n = 1: 1 is the trivial solution.
2 <= n < 4: no doubly centrosymmetric solutions exist.
n = 4: 2413 is the first and only solution.
.*..
...*
*...
..*.
n = 5: 25314 is the first and only solution.
6 <= n < 12: no doubly centrosymmetric solutions exist.
Triangle starts:
1;
0, 0;
0, 0, 0;
2, 4, 1, 3;
2, 5, 3, 1, 4;
0, 0, 0, 0, 0, 0;
...


CROSSREFS

Cf. A141843, A260318, A261596, A261597.
Sequence in context: A322169 A332084 A130266 * A211197 A258246 A258240
Adjacent sequences: A261592 A261593 A261594 * A261596 A261597 A261598


KEYWORD

nonn,tabl


AUTHOR

Martin Renner, Aug 25 2015


STATUS

approved



