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 A348077 Starts of runs of 3 consecutive numbers that have an equal number of even and odd exponents in their prime factorization (A187039). 4
 603, 1250, 1323, 2523, 4203, 4923, 4948, 7442, 10467, 12591, 18027, 20402, 21123, 23823, 31507, 31850, 36162, 40327, 54475, 54511, 55323, 58923, 63747, 64386, 71523, 73204, 79011, 83151, 85291, 88047, 97675, 103923, 104211, 118323, 120787, 122571, 124891, 126927 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE 603 is a term since 603 = 3^2 * 67, 603 + 1 = 604 = 2^2 * 151 and 603 + 2 = 605 = 5 * 11^2 all have one even and one odd exponent in their prime factorization. MATHEMATICA q[n_] := n == 1 || Count[(e = FactorInteger[n][[;; , 2]]), _?OddQ] == Count[e, _?EvenQ]; v = q /@ Range[3]; seq = {}; Do[v = Append[Drop[v, 1], q[k]]; If[And @@ v, AppendTo[seq, k - 2]], {k, 4, 130000}]; seq PROG (Python) from sympy import factorint def aupto(limit): alst, condvec = [], [False, False, False] for kp2 in range(4, limit+3): evenodd = [0, 0] for e in factorint(kp2).values(): evenodd[e%2] += 1 condvec = condvec[1:] + [evenodd[0] == evenodd[1]] if all(condvec): alst.append(kp2-2) return alst print(aupto(126927)) # Michael S. Branicky, Sep 27 2021 CROSSREFS Subsequence of A187039 and A348076. Sequence in context: A218521 A145331 A252957 * A066785 A178032 A107256 Adjacent sequences: A348074 A348075 A348076 * A348078 A348079 A348080 KEYWORD nonn AUTHOR Amiram Eldar, Sep 27 2021 STATUS approved

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Last modified April 15 12:17 EDT 2024. Contains 371681 sequences. (Running on oeis4.)