A366534 The number of unitary divisors of the exponentially odd numbers (A268335).

1, 2, 2, 2, 4, 2, 2, 4, 2, 2, 4, 4, 2, 2, 4, 4, 2, 4, 4, 2, 2, 8, 2, 2, 4, 4, 4, 2, 4, 4, 4, 2, 8, 2, 4, 2, 4, 2, 4, 4, 4, 4, 4, 2, 2, 4, 4, 8, 2, 4, 8, 2, 2, 4, 4, 8, 2, 4, 2, 4, 4, 4, 4, 2, 4, 4, 4, 4, 4, 2, 2, 8, 2, 4, 8, 4, 2, 2, 8, 4, 2, 8, 4, 4, 4, 8, 4

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A034444(A268335(n)).

Mathematica

f[n_] := Module[{e = FactorInteger[n][[;; , 2]]}, If[AllTrue[e, OddQ], 2^Length[e], Nothing]]; f[1] = 1; Array[f, 150]

Prog

(PARI) lista(max) = for(k = 1, max, my(e = factor(k)[, 2], isexpodd = 1); for(i = 1, #e, if(!(e[i] % 2), isexpodd = 0; break)); if(isexpodd, print1(2^(#e), ", ")));

Crossrefs

Cf. A034444, A077610, A268335, A366438, A366535.

Similar sequences: A366536, A366538.

Sequence in context: A049716 A361289 A188903 * A066671 A159802 A329586

Adjacent sequences: A366531 A366532 A366533 * A366535 A366536 A366537

Keyword

nonn,easy

Author

Amiram Eldar, Oct 12 2023

Status

approved