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 A274972 Numbers x such that there exists n in N : (x+1)^3 - x^3 = 61*n^2. 3
 4, 4387, 4273420, 4162307179, 4054082919412, 3948672601200595, 3846003059486460604, 3746003031267211428187, 3648603106451204444594020, 3553735679680441861823147779, 3461334903405643922211301343212, 3371336642181417499791945685141195 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Colin Barker, Table of n, a(n) for n = 1..300 Index entries for linear recurrences with constant coefficients, signature (975,-975,1). FORMULA G.f.: x*(4+487*x-5*x^2) / ((1-x)*(1-974*x+x^2)). a(n) = 975*a(n-1)-975*a(n-2)+a(n-3) for n>3. a(n) = (-6-(27+2*sqrt(183))*(487+36*sqrt(183))^(-n)+(-27+2*sqrt(183))*(487+36*sqrt(183))^n)/12. EXAMPLE 4387 is in the sequence because ((4387+1)^3-4387^3)/61 = 946729 = 973^2. PROG (PARI) Vec(x*(4+487*x-5*x^2)/((1-x)*(1-974*x+x^2)) + O(x^20)) (PARI) isok(x) = issquare(((x+1)^3-x^3)/61) CROSSREFS Cf. A145336, A145212, A274971, A275060. Sequence in context: A249804 A079682 A127235 * A203036 A102205 A283663 Adjacent sequences:  A274969 A274970 A274971 * A274973 A274974 A274975 KEYWORD nonn,easy AUTHOR Colin Barker, Jul 13 2016 STATUS approved

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Last modified October 15 13:01 EDT 2018. Contains 316236 sequences. (Running on oeis4.)