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Search: id:A144711
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| A144711 |
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Numbers n such that [sum_i=1..r (p(i)^2)]/r = c^2. p(i) prime divisors of n, c integer. |
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+0
1
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| 2, 3, 4, 5, 7, 8, 9, 11, 13, 16, 17, 19, 23, 25, 27, 29, 31, 32, 37, 41, 43, 47, 49, 53, 59, 61, 64, 67, 71, 73, 79, 81, 83, 89, 97, 101, 103, 107, 109, 113, 119, 121, 125, 127, 128, 131, 137, 139, 149, 151, 157, 161, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 211
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A005063(n)/A001221(n) = c^2. Also numbers n such that the RootMeanSquare of prime divisors of n is an integer.
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MAPLE
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A005063 := proc(n) add(p^2, p=numtheory[factorset](n)) ; end: A001221 := proc(n) nops(numtheory[factorset](n)) ; end: isA144711 := proc(n) local sofpr ; sofpr := A001221(n) ; if sofpr <> 0 then issqr(A005063(n)/sofpr) ; else false ; fi; end: for n from 1 to 500 do if isA144711(n) then printf("%d, ", n) ; fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 20 2008]
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CROSSREFS
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Cf. A005063, A001221, A140480
Sequence in context: A137944 A087441 A059046 this_sequence A036116 A000961 A128603
Adjacent sequences: A144708 A144709 A144710 this_sequence A144712 A144713 A144714
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KEYWORD
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easy,nonn
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AUTHOR
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Ctibor O. Zizka (c.zizka(AT)email.cz), Sep 19 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 20 2008
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