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Search: id:A137442
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| A137442 |
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n^2 followed by smallest integer not yet listed. This is a permutation of the positive integers. |
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+0
1
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| 1, 2, 4, 3, 9, 5, 16, 6, 25, 7, 36, 8, 49, 10, 64, 11, 81, 12, 100, 13, 121, 14, 144, 15, 169, 17, 196, 18, 225, 19, 256, 20, 289, 21, 324, 22, 361, 23, 400, 24, 441, 26, 484, 27, 529, 28, 576, 29, 625, 30, 676, 31, 729, 32, 784, 33, 841, 34, 900, 35
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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Formula, generating two terms for every n: n^2, n + round(sqrt(n))
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PROGRAM
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Ruby code, correct to any term:
sk_ct = 2
skip = 4
at = 1
(1..(1.0/0)).each{ |i|
if (at+=1) == skip
at+=1
sk_ct +=1
skip = sk_ct * sk_ct
end
print i*i, " ", at, " "
}
Simpler Ruby code, correct until i is so large that floating point rounding causes errors. I estimate this will be before i reaches 10000000000000000
(1..(1.0/0)).each{ |i|
print i*i, " ", i + (Math.sqrt(i) + 0.5).to_i, " "
}
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CROSSREFS
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Cf. A000463.
Sequence in context: A021045 A063379 A000463 this_sequence A111390 A129596 A060837
Adjacent sequences: A137439 A137440 A137441 this_sequence A137443 A137444 A137445
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KEYWORD
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easy,nonn
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AUTHOR
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Andy Martin (oldadit(AT)gmail.com), Apr 18 2008
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