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 A199514 Numerators of zeros to a symmetric polynomial. Numerators of mu(n)^2*(n/(n - phi(n))). 4
 2, 3, 0, 5, 3, 7, 0, 0, 5, 11, 0, 13, 7, 15, 0, 17, 0, 19, 0, 7, 11, 23, 0, 0, 13, 0, 0, 29, 15, 31, 0, 33, 17, 35, 0, 37, 19, 13, 0, 41, 7, 43, 0, 0, 23, 47, 0, 0, 0, 51, 0, 53, 0, 11, 0, 19, 29, 59, 0, 61, 31, 0, 0, 65, 33, 67, 0, 69, 35, 71, 0, 73, 37, 0, 0, 77, 13, 79, 0, 0, 41, 83, 0, 85, 43, 87, 0, 89, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS The polynomials are defined as the determinant of a symmetric matrix with the following definition: T(n, 1) = 1, T(1, k) = 1, T(n, k) = If n < k, x - Sum_(i = 1)^(i = n - 1) of T(k - i, n), Else x - Sum_(i = 1)^(i = k - 1) of T(k - i, n). Eric Naslund on math stackexchange kindly gave the description in terms of arithmetic functions. The sequence of fractions A199514/A199515 is integer only for prime numbers. As the matrix gets bigger there are fractions as zeros that are greater than small prime numbers. LINKS Antti Karttunen, Table of n, a(n) for n = 2..65537 Mats Granvik, Are the primes found as a subset in this sequence?, math stackexchange. FORMULA A199514(n)/A199515(n) = A008683(n)^2*(n/(n - A000010(n))), n > 1. a(n) = numerator of A008966(n)*(n/A051953(n)). - Antti Karttunen, Sep 07 2018 EXAMPLE The seven times seven symmetric matrix is: 1......1......1......1......1......1......1 1...-1+x......1...-1+x......1...-1+x......1 1......1...-2+x......1......1...-2+x......1 1...-1+x......1.....-1......1...-1+x......1 1......1......1......1...-4+x......1......1 1...-1+x...-2+x...-1+x......1...2-2x......1 1......1......1......1......1......1...-6+x Taking the determinant of the matrix above gives the polynomial: -1260 x + 2322 x^2 - 1594 x^3 + 506 x^4 - 74 x^5 + 4 x^6 The polynomials for the first seven matrices are: 1, -2 + x, 6 - 5 x + x^2, -6 x + 5 x^2 - x^3, 30 x - 31 x^2 + 10 x^3 - x^4, 180 x - 306 x^2 + 184 x^3 - 46 x^4 + 4 x^5, -1260 x + 2322 x^2 - 1594 x^3 + 506 x^4 - 74 x^5 + 4 x^6, ... and their zeros respectively are: {} 2 2, 3 2, 3, 0 2, 3, 0, 5 2, 3, 0, 5, 3/2 2, 3, 0, 5, 3/2, 7 ... MATHEMATICA Table[Numerator[MoebiusMu[n]^2*(n/(n - EulerPhi[n]))], {n, 2, 90}] (* or *) Clear[nn, t, n, k, M, x]; nn = 90; a = Range[nn]*0; Do[ 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]]; M = Table[Table[t[n, k], {k, 1, i}], {n, 1, i}]; a[[i]] = x /. Solve[Det[M] == 0, x], {i, 1, nn}]; a[[1]] = {}; b = Differences[Table[Total[a[[i]]], {i, 1, nn}]]; Numerator[b] PROG (PARI) A199154(n) = numerator(issquarefree(n)*(n/(n-eulerphi(n)))); \\ Antti Karttunen, Sep 07 2018 CROSSREFS Cf. A000010, A008683, A008966, A051953, A191898. Denominators: A199515. Sequence in context: A080368 A057174 A197658 * A080367 A066913 A090303 Adjacent sequences:  A199511 A199512 A199513 * A199515 A199516 A199517 KEYWORD nonn,frac,easy AUTHOR Mats Granvik, Nov 07 2011 STATUS approved

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Last modified May 21 17:33 EDT 2019. Contains 323444 sequences. (Running on oeis4.)