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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 (list; graph; refs; listen; history; text; internal format)
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

Zhi-Wei 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

Zhi-Wei Sun, Aug 25 2013

STATUS

approved

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Last modified June 25 10:28 EDT 2021. Contains 345453 sequences. (Running on oeis4.)