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A283050
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Integers that are divisible by the square of their least prime factor.
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12
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4, 8, 9, 12, 16, 20, 24, 25, 27, 28, 32, 36, 40, 44, 45, 48, 49, 52, 56, 60, 63, 64, 68, 72, 76, 80, 81, 84, 88, 92, 96, 99, 100, 104, 108, 112, 116, 117, 120, 121, 124, 125, 128, 132, 135, 136, 140, 144, 148, 152, 153, 156, 160, 164, 168, 169, 171, 172, 175, 176, 180
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OFFSET
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1,1
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COMMENTS
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Integers > 1 such that A126773(n) = 1.
Conjecture: 1 <= a(n+1) - a(n) <= 4. - R. J. Cano, Feb 27 2017
The conjecture is true since all multiples of 4 are in this sequence. - Charles R Greathouse IV, Feb 28 2017
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LINKS
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Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
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FORMULA
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a(n) ~ kn where 1/k = 1/2^2 + 1/2*1/3^2 + 1/2*2/3*1/5^2 + 1/2*2/3*4/5*1/7^2 + ... = A283071 so k = 3.02940306.... - Charles R Greathouse IV, Feb 27 2017
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MAPLE
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A283050 := proc(n)
option remember;
if n =1 then
4 ;
else
for a from procname(n-1)+1 do
if A126773(a)= 1 then
return a;
end if;
end do:
end if;
end proc:
seq(A283050(n), n=1..100) ; # R. J. Mathar, Mar 03 2017
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MATHEMATICA
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Select[Range[2, 180], Divisible[#, FactorInteger[#][[1, 1]]^2] &] (* Michael De Vlieger, Feb 27 2017 *)
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PROG
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(PARI) isok(n) = !(n % factor(n)[1, 1]^2);
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CROSSREFS
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Subsequence of A013929 (numbers that are not squarefree).
Cf. A126773, A283071.
Sequence in context: A034030 A057109 A069189 * A069168 A102211 A244032
Adjacent sequences: A283047 A283048 A283049 * A283051 A283052 A283053
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KEYWORD
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nonn
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AUTHOR
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Michel Marcus, Feb 27 2017
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STATUS
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approved
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