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A107925
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Odd numbers n such that n^2 is an arithmetic number.
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1
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1, 7, 13, 19, 31, 37, 43, 61, 67, 73, 79, 91, 97, 103, 109, 121, 127, 133, 139, 151, 157, 163, 181, 193, 199, 211, 217, 223, 229, 241, 247, 259, 271, 277, 283, 301, 307, 313, 331, 337, 349, 367, 373, 379, 397, 403, 409, 421, 427, 433, 439, 457, 463, 469, 481
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OFFSET
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1,2
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COMMENTS
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Also, odd numbers n such that the arithmetic and geometric means of the divisors of n^2 are both integer.
Even numbers with this property are more rare and given by A107924.
Contains A002476 as a subsequence.
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LINKS
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Table of n, a(n) for n=1..55.
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MATHEMATICA
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Select[Range[1, 500, 2], Mod[DivisorSigma[1, #^2], DivisorSigma[0, #^2]]==0&]
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CROSSREFS
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Cf. A003601, A107924.
Sequence in context: A038590 A218146 A129389 * A002476 A123365 A144921
Adjacent sequences: A107922 A107923 A107924 * A107926 A107927 A107928
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KEYWORD
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easy,nonn
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AUTHOR
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Zak Seidov, Jun 10 2005
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STATUS
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approved
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