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A248150
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Numbers whose sum of divisors (A000203) is divisible by 4.
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11
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3, 6, 7, 11, 12, 14, 15, 19, 21, 22, 23, 24, 27, 28, 30, 31, 33, 35, 38, 39, 42, 43, 44, 46, 47, 48, 51, 54, 55, 56, 57, 59, 60, 62, 63, 65, 66, 67, 69, 70, 71, 75, 76, 77, 78, 79, 83, 84, 85, 86, 87, 88, 91, 92, 93, 94, 95, 96, 99, 102, 103, 105, 107, 108, 110, 111, 112, 114, 115, 118
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OFFSET
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1,1
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COMMENTS
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A subsequence of A028983 (even sum of divisors) which contains all numbers but the squares and twice the squares, so no term of this sequence is of that form, either.
Any number having at least two odd prime factors to an odd power is in this sequence, therefore it has asymptotic density 1. - M. F. Hasler, Apr 26 2017
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LINKS
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FORMULA
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MATHEMATICA
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Select[Range[200], Divisible[DivisorSigma[1, #], 4]&] (* Harvey P. Dale, Feb 20 2015 *)
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PROG
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(PARI) for(n=1, 999, sigma(n)%4||print1(n", "))
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CROSSREFS
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First differs from A022544 by including 65.
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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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