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A056534
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Mapping from the ordering by product (A027750, A056538) to the ordering by sum (A002260, A004736) of ordered pairs (a,b), a>=1, b>=1.
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4
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1, 2, 3, 4, 6, 7, 5, 10, 11, 15, 16, 8, 9, 21, 22, 28, 29, 12, 14, 36, 37, 13, 45, 46, 17, 20, 55, 56, 66, 67, 23, 18, 19, 27, 78, 79, 91, 92, 30, 35, 105, 106, 24, 26, 120, 121, 38, 25, 44, 136, 137, 153, 154, 47, 31, 34, 54, 171, 172, 190, 191, 57, 32, 33, 65, 210, 211, 39
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Index entries for sequences that are permutations of the natural numbers
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EXAMPLE
| The "ordering by sum": (1,1),(1,2),(2,1),(1,3),(2,2),(3,1),(1,4),(2,3),(3,2),(4,1),...
The "ordering by product": (1,1),(1,2),(2,1),(1,3),(3,1),(1,4),(2,2),(4,1),(1,5),(5,1),...
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MAPLE
| ordered_pair_perm := proc(upto_n) local a, i, j; a := []; for i from 1 to upto_n do for j in sort(divisors(i)) do a := [op(a), binomial(((i/j) + j - 1), 2)+j]; od; od; RETURN(a); end;
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CROSSREFS
| Inverse: A056535.
Sequence in context: A026236 A048201 A186004 * A130264 A072659 A072766
Adjacent sequences: A056531 A056532 A056533 * A056535 A056536 A056537
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KEYWORD
| nonn
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AUTHOR
| Antti Karttunen Jun 20, 2000
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