OFFSET
0,2
COMMENTS
The odd part of a number is its largest odd divisor (A000265), phi is Euler's totient function (A000010). - Alonso del Arte, Oct 13 2013
FORMULA
a(n) = smallest m such that A227944(m)=n.
EXAMPLE
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.
PROG
(Haskell)
import Data.List (elemIndex); import Data.Maybe (fromJust)
a227946 = (+ 1) . fromJust . (`elemIndex` a227944_list)
-- Reinhard Zumkeller, Nov 10 2013
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Max Alekseyev, Oct 03 2013
EXTENSIONS
a(15) through a(21) copied over from A049117 by Max Alekseyev, Oct 13 2013
STATUS
approved