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A227946
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Smallest m such that the number of iterations of "take odd part of phi" to reach 1 from m (A227944) is n.
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4
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1, 2, 7, 19, 47, 163, 487, 1307, 2879, 19683, 39367, 177147, 531441, 1594323, 4782969, 14348907, 43046721, 86093443, 258280327, 688747547, 3486784401, 10460353203
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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a(n) = smallest m such that A227944(m)=n.
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EXAMPLE
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a(1) = 2 because just one step is needed to reach 1 from 2, since phi(2) = 1. The numbers 3, 4, 5 and 6 also take one step.
a(2) = 7 because two steps are needed to reach 1 from 7: phi(7) = 6, the odd part of which is 3, and phi(3) = 2, the odd part of which is 1. The numbers from 8 to 18 take one or two steps to reach 1.
a(3) = 19 because three steps are needed to reach 1 from 19: phi(19) = 18, the odd part of which is 9, and phi(9) = 6, the odd part of which is 3, and phi(3) = 2, the odd part of which is 1.
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PROG
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(Haskell)
import Data.List (elemIndex); import Data.Maybe (fromJust)
a227946 = (+ 1) . fromJust . (`elemIndex` a227944_list)
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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