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A337343
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Numbers k such that A064989(sigma(k)) >= k.
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2
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1, 2, 4, 9, 16, 18, 25, 36, 50, 64, 100, 144, 225, 256, 289, 400, 450, 576, 578, 729, 784, 900, 1024, 1156, 1296, 1458, 1600, 1681, 1764, 1800, 1936, 2304, 2401, 2601, 2704, 2916, 3136, 3362, 3481, 3600, 4096, 4356, 4624, 4802, 4900, 5041, 5184, 5202, 5328, 5776, 5832, 6084, 6400, 6561, 6724, 6962, 7056, 7225, 7744, 7921, 8192
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OFFSET
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1,2
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COMMENTS
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Not all terms are squares or twice squares: the first terms not in A028982 are: 5328, 8784, 22608, 27792, 35136, 39888, 45072, 57168, 58320, 60624, ...
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LINKS
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PROG
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(PARI)
A064989(n) = {my(f); f = factor(n); if((n>1 && f[1, 1]==2), f[1, 2] = 0); for (i=1, #f~, f[i, 1] = precprime(f[i, 1]-1)); factorback(f)};
isA337343(n) = (A064989(sigma(n))>=n);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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