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Search: id:A073713
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| A073713 |
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Numbers n such that the number of distinct primes dividing n = number of anti-divisors of n. |
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+0
2
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| 1, 3, 4, 12, 24, 30, 36, 114, 120, 156, 174, 516, 576, 744, 804, 834, 894, 1056, 1344, 1356, 1626, 1686, 1884, 2064, 2136, 2274, 2616, 3396, 3414, 3606, 4044, 4146, 4314, 4506, 5034, 5136, 6036, 6054, 6126, 6306, 6504, 7296, 7680, 7824, 7944, 8994, 9024
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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See A066272 for definition of anti-divisor.
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EXAMPLE
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30 is here since it has three distinct primes that divide it: {2, 3, 5} and three anti-divisors: {4, 12, 20}.
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PROGRAM
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(PARI) {for(n=1, 9050, v1=[]; v2=[]; v3=[]; ds=divisors(2*n-1); for(k=2, matsize(ds)[2]-1, if(ds[k]%2>0, v1=concat(v1, ds[k]))); ds=divisors(2*n); for(k=2, matsize(ds)[2]-1, if(ds[k]%2>0, v2=concat(v2, ds[k]))); ds=divisors(2*n+1); for(k=2, matsize(ds)[2]-1, if(ds[k]%2>0, v3=concat(v3, ds[k]))); v=vecsort(concat(v1, concat(v2, v3))); if(matsize(v)[2]==matsize(factor(n))[1], print1(n, ", ")))}
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CROSSREFS
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Cf. A001221, A066272.
Sequence in context: A111358 A111357 A081621 this_sequence A084921 A070765 A000577
Adjacent sequences: A073710 A073711 A073712 this_sequence A073714 A073715 A073716
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KEYWORD
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nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Aug 30 2002
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EXTENSIONS
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Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Sep 02 2002
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