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A063991
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Unitary amicable numbers.
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28
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114, 126, 1140, 1260, 18018, 22302, 32130, 40446, 44772, 49308, 56430, 64530, 67158, 73962, 142310, 168730, 180180, 197340, 223020, 241110, 242730, 286500, 296010, 308220, 365700, 429750, 462330, 548550, 591030, 618570, 669900, 671580, 739620, 785148, 815100, 827652, 827700, 932100
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OFFSET
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1,1
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COMMENTS
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The concept of unitary amicable numbers was introduced by Wall (1970), who proved that both members of a pair are either odd or even, and found 610 pairs (only 592 were correct, as found by te Riele, 1978).
Hagis (1971) calculated the first 19 pairs (the terms below 10^6).
Najar (1995) calculated the first 185 pairs (terms whose smaller member is below 10^8). (End)
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REFERENCES
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Mariano Garcia, New unitary amicable couples, J. Recreational Math., Vol. 17, No. 1 (1984-5), pp. 32-35.
M. Lal, G. Tiller, and T. Summers, Unitary sociable numbers, Proceedings of the Second Manitoba Conference on Numerical Mathematics, Congressus Numerantium No. 7, 1972, pp. 211-216.
Clifford A. Pickover, The Math Book, Sterling, NY, 2009; see p. 90.
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LINKS
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Rudolph M. Najar, The Unitary Amicable Pairs To 10^8, International Journal of Mathematics and Mathematical Sciences, Volume 18, No. 2 (1995), pp. 405-410, Article ID 396507, 6 pages.
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PROG
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(PARI) f(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)) - n;
isok1(n) = iferr(f(n) == n, E, 0);
isok2(n) = iferr(f(f(n)) == n, E, 0);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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