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 A259749 Numbers that are congruent to {1,2,5,7,10,11,13,17,19,23} mod 24. 6
 1, 2, 5, 7, 10, 11, 13, 17, 19, 23, 25, 26, 29, 31, 34, 35, 37, 41, 43, 47, 49, 50, 53, 55, 58, 59, 61, 65, 67, 71, 73, 74, 77, 79, 82, 83, 85, 89, 91, 95, 97, 98, 101, 103, 106, 107, 109, 113, 115, 119, 121, 122, 125, 127, 130, 131, 133, 137, 139, 143, 145 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Original name: Numbers n such that A259748(n) = 0. LINKS Danny Rorabaugh, Table of n, a(n) for n = 1..10000 Index entries for linear recurrences with constant coefficients, signature (2,-2,2,-2,2,-2,2,-2,2,-1). FORMULA A259748(a(n)) = Sum_{x*y: x,y in Z/a(n)Z, x<>y} = 0. G.f.: x*(1+x^2)*(1+2*x^2-x^3+2*x^4-2*x^5+3*x^6+x^7) / ((1-x)^2*(1-x+x^2-x^3+x^4)*(1+x+x^2+x^3+x^4)). - Colin Barker, Aug 25 2016 MATHEMATICA A[n_] := A[n] = Sum[a b, {a, 1, n}, {b, a + 1, n}] ; Select[Range[600], Mod[A[#], #]  == 0 & ] Rest@ CoefficientList[Series[x (1 + x^2) (1 + 2 x^2 - x^3 + 2 x^4 - 2 x^5 + 3 x^6 + x^7)/((1 - x)^2*(1 - x + x^2 - x^3 + x^4) (1 + x + x^2 + x^3 + x^4)), {x, 0, 61}], x] (* Michael De Vlieger, Aug 25 2016 *) PROG (PARI) Vec(x*(1+x^2)*(1+2*x^2-x^3+2*x^4-2*x^5+3*x^6+x^7)/((1-x)^2*(1-x+x^2-x^3+x^4)*(1+x+x^2+x^3+x^4)) + O(x^100)) \\ Colin Barker, Aug 25 2016 CROSSREFS Cf. A000914. Other sequences of numbers n such that A259748(n)/n equals a constant: A008606, A073762, A259750, A259751, A259752, A259754, A259755. Sequence in context: A099477 A261034 A330777 * A067934 A284470 A112730 Adjacent sequences:  A259746 A259747 A259748 * A259750 A259751 A259752 KEYWORD nonn,easy AUTHOR José María Grau Ribas, Jul 04 2015 EXTENSIONS Better name from Danny Rorabaugh, Oct 22 2015 STATUS approved

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Last modified October 1 13:04 EDT 2020. Contains 337443 sequences. (Running on oeis4.)