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Search: id:A063936
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| A063936 |
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Sum of unitary proper divisors of n is a square > 1. |
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+0
2
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| 15, 26, 44, 56, 95, 96, 119, 122, 124, 140, 143, 194, 215, 216, 236, 287, 304, 364, 386, 407, 495, 511, 527, 551, 556, 560, 575, 639, 740, 752, 764, 780, 791, 794, 815, 871, 900, 935, 936, 992, 1004, 1036, 1116, 1159, 1196, 1199, 1232, 1295, 1328, 1346
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A unitary divisor of n is a divisor d of n such that gcd(d,n/d)=1.
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
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EXAMPLE
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The unitary divisors of 15 are 1,3,5,15 and then the unitary aliquot part is 9 which is a square.
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PROGRAM
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(PARI) us(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)); j=[]; for(n=1, 3000, if(us(n)-n > 1 && issquare(us(n)-n), j=concat(j, n))); j
(PARI) us(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)) { n=0; for (m=1, 10^9, u=us(m) - m; if (issquare(u) && u > 1, write("b063936.txt", n++, " ", m); if (n==1000, break)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 03 2009]
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CROSSREFS
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Cf. A034448, A063937.
Sequence in context: A050700 A139566 A097963 this_sequence A132452 A063552 A131541
Adjacent sequences: A063933 A063934 A063935 this_sequence A063937 A063938 A063939
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KEYWORD
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easy,nonn
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AUTHOR
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Felice Russo (felice.russo(AT)katamail.com), Aug 31 2001
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EXTENSIONS
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More terms from Jason Earls (zevi_35711(AT)yahoo.com), Sep 04 2001
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