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A053226
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Numbers k for which sigma(k) > sigma(k+1).
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18
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4, 6, 8, 10, 12, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 45, 46, 48, 50, 52, 54, 56, 58, 60, 64, 66, 68, 70, 72, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 105, 106, 108, 110, 112, 114, 116, 117, 118, 120, 122, 124, 126, 128, 130
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OFFSET
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1,1
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COMMENTS
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The asymptotic density of this sequence is 1/2 (Erdős, 1936). - Amiram Eldar, Mar 19 2021
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LINKS
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MAPLE
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with(numtheory): seq( `if`((sigma(i) > sigma(i+1)), i, print( )), i=1..139);
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MATHEMATICA
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Select[Range[150], DivisorSigma[1, #] > DivisorSigma[1, # + 1] &] (* Carl Najafi, Aug 16 2011 *)
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PROG
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(Haskell)
import Data.List (findIndices)
a053226 n = a053226_list !! (n-1)
a053226_list = map (+ 1) $ findIndices (< 0) a053222_list
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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