

A303809


Multiplicative with a(p^k) = 2^a(k).


3



1, 2, 2, 4, 2, 4, 2, 4, 4, 4, 2, 8, 2, 4, 4, 16, 2, 8, 2, 8, 4, 4, 2, 8, 4, 4, 4, 8, 2, 8, 2, 4, 4, 4, 4, 16, 2, 4, 4, 8, 2, 8, 2, 8, 8, 4, 2, 32, 4, 8, 4, 8, 2, 8, 4, 8, 4, 4, 2, 16, 2, 4, 8, 16, 4, 8, 2, 8, 4, 8, 2, 16, 2, 4, 8, 8, 4, 8, 2, 32, 16, 4, 2, 16
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OFFSET

1,2


COMMENTS

This sequence contains every power of 2; see A303819 for the corresponding least indices.
For any n > 0, a(n) only depends on the prime signature of n.


LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..10000


FORMULA

a(n) <= n with equality iff n = A014221(k) for some k >= 0.
a(A002110(k)) = 2^k for any k >= 0.
a(n) = 2 iff n is prime.


PROG

(PARI) a(n) = my (f=factor(n)); prod (i=1, #f~, 2^a(f[i, 2]))


CROSSREFS

Cf. A002110, A014221, A061142, A303819.
Sequence in context: A040003 A106469 A082508 * A193562 A249868 A255311
Adjacent sequences: A303806 A303807 A303808 * A303810 A303811 A303812


KEYWORD

nonn,easy,mult


AUTHOR

Rémy Sigrist, Apr 30 2018


STATUS

approved



