cp's OEIS Frontend

A280801 Least k > 0 such that (2*n)^k is in A002202, or 0 if no such k exists.

%I A280801 #32 Jan 14 2017 08:09:23
%S A280801 1,1,1,1,1,1,2,1,1,1,1,1,2,1,1,1,4,1,3,1,1,1,1,1,2,1,1,1,1,1,5,1,1,2,
%T A280801 1,1,2,3,1,1,1,1,15,1,2,1,2,1,3,1,1,1,1,1,1,1,2,1,3,1,7,2,1,1,1,1,2,1,
%U A280801 1,1,3,1,2,1,1,3,3,1,8,1,1,1,1,1,2,1,2,1,1,1,4,1,2,2,1,1,4,1,1,1,17,1,2,1,1,1,3,1,3,1,1,1,1,1,2,1,2,2,1,1,2,5,2,2,1,1,4,1,3
%N A280801 Least k > 0 such that (2*n)^k is in A002202, or 0 if no such k exists.
%C A280801 Least k such that A280801(k) = n, or 0 if no such k exists are 1, 7, 19, 17, 31, 223, 61, 79, 151, 383, 181, 347, 523, 1109, 43, 607, 101, 733, 1033, 409, 1783, 1123, 199, 1471, 1301, 5113, 1801, 2311, 3617, 1699, 1543, 7489, 2663, 4583, 7829, 2749, 4177, 5179, 2389, 13291, 20389, ...
%C A280801 What is the asymptotic behavior of this sequence?
%C A280801 Conjecture: a(n) > 0 for all values of n. - _Altug Alkan_, Jan 11 2017
%H A280801 Giovanni Resta, <a href="/A280801/b280801.txt">Table of n, a(n) for n = 1..1000</a>
%F A280801 a(n) = 1 for n in A002180; a(n) <> 1 for n in A079695. - _Michel Marcus_, Jan 08 2017
%e A280801 a(43) = 15 because (43*2)^k is not in A002202 for 0 < k < 15 and 86^15 = 104106241746467411129608011776 is in A002202.
%o A280801 (PARI) a(n) = {my(k = 1); while (!istotient((2*n)^k), k++); k; }
%Y A280801 Cf. A000010, A002180, A002202, A079695.
%K A280801 nonn
%O A280801 1,7
%A A280801 _Altug Alkan_, Jan 08 2017