%I #7 Sep 01 2023 15:23:57

%S 3,27,315,3003,42757,72765,195195,799425,13873275,18131225

%N Odd numbers k such that k is a multiple of A243071(k).

%o (PARI)

%o A243071(n) = if(n<=2, n-1, my(f=factor(n), p, p2=1, res=0); for(i=1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p*p2*(2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); ((3<<#binary(res\2))-res-1)); \\ (Combining programs given in A156552 and A054429)

%o isA364965(n) = ((n>1)&&(n%2)&&!(n%A243071(n)));

%Y Odd terms in A364964.

%Y Sequence A163511(A364495(n)), for n>1, sorted into ascending order.

%Y Cf. A243071.

%Y Cf. also A364498, A364551.

%K nonn,more

%O 1,1

%A _Antti Karttunen_, Sep 01 2023