

A228549


Determinant of the n X n matrix with (i,j)entry equal to 1 or 0 according as i + j is squarefree or not.


5



1, 1, 2, 3, 2, 1, 5, 25, 20, 16, 7, 23, 39, 25, 309, 455, 901, 2168, 920, 1047, 2302, 1536, 3272, 161162, 289493, 529263, 1418949, 1562590, 579999, 15145, 5844471, 5244416, 65749104, 176617384, 2077411081, 7381004327, 10211507191, 10333531933, 7086785521, 8502336136
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OFFSET

1,3


COMMENTS

Conjecture: a(n) is always nonzero. Moreover, a(n)^(1/n) tends to infinity.
We have verified that a(n) is nonzero for all n <= 500.


LINKS

ZhiWei Sun, Table of n, a(n) for n = 1..200


EXAMPLE

a(1) = 1 since 1 + 1 = 2 is squarefree.


MATHEMATICA

a[n_]:=a[n]=Det[Table[If[SquareFreeQ[i+j]==True, 1, 0], {i, 1, n}, {j, 1, n}]]
Table[a[n], {n, 1, 20}]


CROSSREFS

Cf. A005117, A228548, A069191, A228552.
Sequence in context: A238165 A081316 A226362 * A079893 A324646 A286156
Adjacent sequences: A228546 A228547 A228548 * A228550 A228551 A228552


KEYWORD

sign


AUTHOR

ZhiWei Sun, Aug 25 2013


STATUS

approved



