%I #56 Mar 02 2015 15:49:26

%S 2,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,5,1,2,2,1,2,1,6,1,1,2,5,1,1,1,1,1,

%T 8,34,8,1,2,1,10,1,2,350,2,1,111,4,1,3,16,4,15,28,3,1,206,3,10,2,1,1,

%U 2,3,1,15,637,12,1,4,22,17,104,4,2,1012,1,1

%N a(n) = least k such that k * n is in A072226, or 0 if no such k exists.

%C Conjecture: a(n) > 0 for all n.

%C Numbers n such that n * a(n) > 10^5, a(n) is currently unknown for n = 121, 124, 130, 143, 144, 162, 164, 171, 172, 185, 188, 197, 201, 215, ...

%C a(121) = (A117545(2048))/11 and they are both currently unknown.

%C A117545(2^n) = a(A064549(n)).

%H Eric Chen, <a href="/A250209/b250209.txt">Table of n, a(n) for n = 1..120</a>

%H Eric Chen, <a href="/A250209/a250209_1.txt">Table of n, a(n) for n = 1..300 status</a>

%t Table[k=1; while[!PrimeQ[Cyclotomic[n*k, 2]], k++]; k, {n, 150}]

%o (PARI) a(n) = {k = 1; while (!isprime(polcyclo(k*n, 2)), k++); k;} \\ _Michel Marcus_, Jan 18 2015

%K nonn

%O 1,1

%A _Eric Chen_, Jan 18 2015