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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
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
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
KEYWORD
nonn,easy,mult
AUTHOR
Rémy Sigrist, Apr 30 2018
STATUS
approved