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A249917
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Square array read by antidiagonals where the n-th row lists the integers x such that gcd(x, sigma(x)) = n.
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1
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1, 2, 10, 3, 14, 15, 4, 20, 18, 12, 5, 22, 33, 44, 95, 7, 26, 45, 48, 145, 6, 8, 34, 51, 76, 200, 30, 91, 9, 38, 69, 88, 295, 42, 196, 56, 11, 46, 72, 92, 395, 54, 273, 112, 153, 13, 52, 87, 108, 445, 66, 287, 184, 288, 40, 16, 58, 99, 124, 475, 78, 455, 248, 459, 190, 473
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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First line is A014567 and first column is A074391.
This is a permutation of the positive integers.
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LINKS
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Table of n, a(n) for n=1..66.
Index entries for sequences that are permutations of the natural numbers
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EXAMPLE
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Array begins:
1, 2, 3, 4, 5, 7, 8, ...
10, 14, 20, 22, 26, 34, 38, ...
15, 18, 33, 45, 51, 69, 72, ...
12, 44, 48, 76, 88, 92, 108, ...
95, 145, 200, 295, 395, 445, 475, ...
6, 30, 42, 54, 66, 78, 102, ...
91, 196, 273, 287, 455, 581, 637, ...
56, 112, 184, 248, 368, 376, 432, ...
...
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PROG
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(PARI) triangle(nn) = {v = vector(nn); for (n=1, nn, for (k=1, n, if (! v[k], x = 1, x = v[k] + 1); while (gcd(sigma(x), x) != k, x++); print1(x, ", "); v[k] = x; ); print(); ); }
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CROSSREFS
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Cf. A009194 (gcd(n, sigma(n))), A014567 (gcd(n, sigma(n))=1), A074391 (smallest x such that gcd(x, sigma(x)) is n),
Sequence in context: A239136 A239137 A252758 * A176577 A247476 A245062
Adjacent sequences: A249914 A249915 A249916 * A249918 A249919 A249920
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KEYWORD
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nonn,tabl
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AUTHOR
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Michel Marcus, Jan 14 2015
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STATUS
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approved
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