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 A069838 Let M_k be the k X k matrix, M_(i,j) = 1 if i^2 + j^2 is squarefree, M_(i,j) = 0 otherwise; sequence gives values of k such that det(M_k) = 0. 1
 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 20, 23, 27, 29, 30, 31, 32, 34, 35, 36, 37, 38, 39, 46, 47, 48, 49, 50, 57, 58, 59, 65, 66, 67, 68, 69, 70, 71, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS No more terms <= 1100. - David A. Corneth, Apr 05 2020 LINKS Jinyuan Wang, Table of n, a(n) for n = 1..67 PROG (PARI) for(n=1, 71, if(matdet(matrix(n, n, i, j, issquarefree(i^2+j^2)))==0, print1(n", "))) CROSSREFS Cf. A005117. Sequence in context: A250048 A051053 A178868 * A067901 A115840 A371565 Adjacent sequences: A069835 A069836 A069837 * A069839 A069840 A069841 KEYWORD nonn AUTHOR Benoit Cloitre, Apr 21 2002 EXTENSIONS More terms from Jinyuan Wang, Apr 05 2020 STATUS approved

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Last modified August 7 14:20 EDT 2024. Contains 375013 sequences. (Running on oeis4.)