A365408 Numbers j whose largest divisor <= sqrt(j) is not a power of 2.

9, 12, 15, 18, 21, 25, 27, 30, 33, 35, 36, 39, 40, 42, 45, 48, 49, 50, 51, 54, 55, 56, 57, 60, 63, 65, 66, 69, 70, 75, 77, 78, 81, 84, 85, 87, 90, 91, 93, 95, 98, 99, 100, 102, 105, 108, 110, 111, 114, 115, 117, 119, 120, 121, 123, 125, 126, 129, 130, 132, 133, 135, 138, 140, 141, 143, 144, 145, 147, 150, 153

Offset: 1

Author

Omar E. Pol, Oct 14 2023

Keywords

• nonn

Comments

Also indices of terms in A033676 that are not a power of 2.

Differs from A342082 in not having {24, 72, 80, 96, 112, ...}. - Hugo Pfoertner, Oct 15 2023

Links

• Paolo Xausa, Table of n, a(n) for n = 1..10000

Crossrefs

Complement of A365406.

Cf. A033676, A057716, A342082.

Programs

Mathematica

A365408Q[n_]:=With[{d=Divisors[n]},!IntegerQ[Log2[d[[Ceiling[Length[d]/2]]]]]];
Select[Range[200],A365408Q] (* Paolo Xausa, Oct 19 2023 *)

Python

from itertools import count, islice
from sympy import divisors
def A365408_gen(startvalue=1): # generator of terms >= startvalue
    return filter(lambda i:(a:=(d:=divisors(i))[len(d)-1>>1])!=1<A365408_list = list(islice(A365408_gen(),30)) # Chai Wah Wu, Oct 18 2023