cp's OEIS Frontend

A261255 Where MU-numbers (cf. A007335) occur in A003586 (3-smooth numbers).

%I A261255 #7 May 15 2025 14:58:33
%S A261255 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 A261255 70,71,72,75,80,83,87,90,92,96,101,104,105,109,113,115,119,123,125,
%U A261255 129,134,138,140,144,145,149,151,156,161,165,166,168,173,178,180
%N A261255 Where MU-numbers (cf. A007335) occur in A003586 (3-smooth numbers).
%H A261255 Reinhard Zumkeller, <a href="/A261255/b261255.txt">Table of n, a(n) for n = 1..1000</a>
%F A261255 A007335(n) = A003586(a(n)).
%e A261255 .   n |   A007335(n)     | a(n) | A003586(a(n))
%e A261255 .  ---+------+-----------+------+--------------
%e A261255 .   1 |    2 |         2 |    2 |            2
%e A261255 .   2 |    3 |         3 |    3 |            3
%e A261255 .   3 |    6 |     2 * 3 |    5 |            6
%e A261255 .   4 |   12 |   2^2 * 3 |    8 |           12
%e A261255 .   5 |   18 |   2 * 3^2 |   10 |           18
%e A261255 .   6 |   24 |   2^3 * 3 |   11 |           24
%e A261255 .   7 |   48 |   2^4 * 3 |   15 |           48
%e A261255 .   8 |   54 |   2 * 3^3 |   16 |           54
%e A261255 .   9 |   96 |   2^5 * 3 |   20 |           96
%e A261255 .  10 |  162 |   2 * 3^4 |   24 |          162
%e A261255 .  11 |  192 |   2^6 * 3 |   25 |          192
%e A261255 .  12 |  216 | 2^3 * 3^3 |   26 |          216 .
%o A261255 (Haskell)
%o A261255 import Data.List (findIndex); import Data.Maybe (fromJust)
%o A261255 a261255 n = fromJust (findIndex (== a007335 n) a003586_list) + 1
%Y A261255  Cf. A007335, A003586.
%K A261255 nonn
%O A261255 1,1
%A A261255 _Reinhard Zumkeller_, Aug 13 2015