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Where MU-numbers (cf. A007335) occur in A003589 (3-smooth numbers).
2

%I #4 Aug 13 2015 02:44:45

%S 2,3,5,8,10,11,15,16,20,24,25,26,31,33,38,39,44,45,47,53,54,57,61,64,

%T 70,71,72,75,80,83,87,90,92,96,101,104,105,109,113,115,119,123,125,

%U 129,134,138,140,144,145,149,151,156,161,165,166,168,173,178,180

%N Where MU-numbers (cf. A007335) occur in A003589 (3-smooth numbers).

%C A007335(n) = A003586(a(n)).

%H Reinhard Zumkeller, <a href="/A261255/b261255.txt">Table of n, a(n) for n = 1..1000</a>

%e . n | A007335(n) | a(n) | A003586(a(n))

%e . ---+------+-----------+------+--------------

%e . 1 | 2 | 2 | 2 | 2

%e . 2 | 3 | 3 | 3 | 3

%e . 3 | 6 | 2 * 3 | 5 | 6

%e . 4 | 12 | 2^2 * 3 | 8 | 12

%e . 5 | 18 | 2 * 3^2 | 10 | 18

%e . 6 | 24 | 2^3 * 3 | 11 | 24

%e . 7 | 48 | 2^4 * 3 | 15 | 48

%e . 8 | 54 | 2 * 3^3 | 16 | 54

%e . 9 | 96 | 2^5 * 3 | 20 | 96

%e . 10 | 162 | 2 * 3^4 | 24 | 162

%e . 11 | 192 | 2^6 * 3 | 25 | 192

%e . 12 | 216 | 2^3 * 3^3 | 26 | 216 .

%o (Haskell)

%o import Data.List (findIndex); import Data.Maybe (fromJust)

%o a261255 n = fromJust (findIndex (== a007335 n) a003586_list) + 1

%Y Cf. A007335, A003586.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Aug 13 2015