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

1,1

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

Mathematica

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

Prog

(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<<a.bit_length()-1, count(max(startvalue, 1)))
A365408_list = list(islice(A365408_gen(), 30)) # Chai Wah Wu, Oct 18 2023

Crossrefs

Complement of A365406.

Cf. A033676, A057716, A342082.

Sequence in context: A235341 A356333 A342082 * A161345 A102655 A308748

Adjacent sequences: A365405 A365406 A365407 * A365409 A365410 A365411

Keyword

nonn

Author

Omar E. Pol, Oct 14 2023

Status

approved