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 A085542 Determinant of the n X n matrix M_(i,j)=i/gcd(i,j)=lcm(i,j)/j. 2
 1, -1, 2, -2, 8, 16, -96, 96, -192, -768, 7680, 15360, -184320, -1105920, -8847360, 8847360, -141557760, -283115520, 5096079360, 20384317440, 244611809280, 2446118092800, -53814598041600, -107629196083200, 430516784332800, 5166201411993600, -10332402823987200 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Determinant of a symmetric polynomial evaluated at x = 1 that starts: {{1, 1, 1, 1, 1}, {1, -1 + x, 1, -1 + x, 1}, {1, 1, -2 + x, 1, 1}, {1, -1 + x, 1, -1, 1}, {1, 1, 1, 1, -4 + x}}. - Mats Granvik, Jul 22 2012 LINKS FORMULA a(n+1)/a(n) = A023900(n+1) the reciprocity balance of n+1. a(n) = Product_{i=1..A000720(n)} (1-A000040(i))^floor(n/A000040(i)). - Enrique Pérez Herrero, Jul 12 2012 MATHEMATICA Clear[nn, t, n, k, M, x]; nnn = 27; a = Range[nnn]*0; Do[nn = ii; t[n_, 1] = 1; t[1, k_] = 1; t[n_, k_] := t[n, k] = If[n < k, If[And[n > 1, k > 1], x - Sum[t[k - i, n], {i, 1, n - 1}], 0], If[And[n > 1, k > 1], x - Sum[t[n - i, k], {i, 1, k - 1}], 0]]; x = 1; M = Table[Table[t[n, k], {k, 1, nn}], {n, 1, nn}]; a[[ii]] = Det[M], {ii, 1, nnn}]; a (* Mats Granvik, Jul 22 2012 *) PROG (PARI) a(n)=matdet(matrix(n, n, i, j, i/gcd(i, j))) CROSSREFS Cf. A000040, A000720, A023900. Sequence in context: A109190 A016120 A188115 * A239682 A009725 A053098 Adjacent sequences: A085539 A085540 A085541 * A085543 A085544 A085545 KEYWORD sign AUTHOR Benoit Cloitre, Aug 19 2003 STATUS approved

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Last modified February 4 11:10 EST 2023. Contains 360055 sequences. (Running on oeis4.)