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Search: id:A113659
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| 1, 9, 25, 49, 57, 65, 81, 85, 93, 121, 133, 153, 169, 185, 201, 209, 217, 225, 253, 261, 289, 297, 301, 305, 309, 329, 333, 345, 361, 369, 381, 385, 393, 417, 441, 469, 477, 489, 497, 501, 505, 513, 525, 529, 533, 553, 561, 565, 581, 621, 625, 633, 637, 645
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Fixed-points of the permutation of the natural numbers given in A111273.
Most odd squares appear to be in this sequence, e.g. 1,9,25,49,81,121,139,... The smallest odd square not appearing is 39^2=1521. - John W. Layman (layman(AT)math.vt.edu), Nov 10 2005. (See A103962.)
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EXAMPLE
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The first nine terms of A111273 are {1,3,2,5,15,7,4,6,9,...}, so 1 and 9 are fixed-points.
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PROGRAM
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(PARI) {m=650; v=Set([]); w=[]; for(k=1, m, d=divisors(k*(k+1)/2); j=1; while(setsearch(v, d[j])>0, j++); a=d[j]; v=setunion(v, Set(a)); w=concat(w, a)); for(n=1, m, if(n==w[n], print1(n, ", ")))}
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CROSSREFS
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Cf. A111273, A113658, A016754, A103962.
Sequence in context: A031036 A051132 A075026 this_sequence A113745 A016754 A110487
Adjacent sequences: A113656 A113657 A113658 this_sequence A113660 A113661 A113662
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KEYWORD
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nonn
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Nov 04 2005
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