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A354258
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Earliest occurrence of n in A354257.
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3
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1, 3, 9, 16, 25, 36, 49, 32, 27, 75, 121, 144, 169, 147, 225, 64, 289, 108, 361, 400, 441, 363, 529, 288, 125, 507, 81, 784, 841, 900, 961, 128, 1089, 867, 1225, 432, 1369, 1083, 1521, 800, 1681, 1764, 1849, 1936, 675, 1587, 2209, 576, 343, 375, 2601, 2704
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OFFSET
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1,2
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COMMENTS
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a(n) is odd if and only if n is odd or n == 2, 10 (mod 12).
a(n) = n^2 if and only if: (a) n is odd or n == 6 (mod 12), and n is squarefree; or (b) n is 4 times an odd squareefree number.
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LINKS
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FORMULA
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a(n) = n * rad(n) if n is odd or n == 6 (mod 12); (3/4) * n * rad(n) if n == 2, 10 (mod 12); 2 * n * rad(n) if n is divisible by 4, where rad = A007947.
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PROG
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(PARI) rad(n) = factorback(factorint(n)[, 1]);
a(n) = n*rad(n)*if(n%2 || n%12==6, 1, if(n%12==2 || n%12==10, 3/4, 2))
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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