login
A117592
a(n) = a(3n) = a(3n+1) = a(3n+2)/2 with a(0)=1.
9
1, 1, 2, 1, 1, 2, 2, 2, 4, 1, 1, 2, 1, 1, 2, 2, 2, 4, 2, 2, 4, 2, 2, 4, 4, 4, 8, 1, 1, 2, 1, 1, 2, 2, 2, 4, 1, 1, 2, 1, 1, 2, 2, 2, 4, 2, 2, 4, 2, 2, 4, 4, 4, 8, 2, 2, 4, 2, 2, 4, 4, 4, 8, 2, 2, 4, 2, 2, 4, 4, 4
OFFSET
0,3
COMMENTS
Row sums of number triangle A117944.
Product of the nonzero digits of (n written in base 3). - Ilya Gutkovskiy, Nov 15 2020
a(n) = 1, 2, 4, 8, 16, 32, 64 iff n is respectively in A005836, A023699, A023700, A023701, A023702, A023703, A023704. - Bernard Schott, Dec 04 2020
LINKS
Felix Fröhlich, Table of n, a(n) for n = 0..10000 (first 2001 terms from Vincenzo Librandi)
FORMULA
a(n) = a(3n)/a(0) = a(3n+1)/a(1) = a(3n+2)/a(2).
a(n) = abs(A117942(n)).
G.f. A(x) satisfies: A(x) = (1 + x + 2*x^2) * A(x^3). - Ilya Gutkovskiy, Nov 15 2020
a(n) = 2^A081603(n). - Kevin Ryde, Nov 15 2020
MATHEMATICA
Nest[ Join[#, #, 2#] &, {1}, 5] (* Robert G. Wilson v, Jul 27 2014 *)
PROG
(PARI) a(n) = 1 << hammingweight(digits(n, 3)>>1); \\ Kevin Ryde, Nov 15 2020
CROSSREFS
See A338882 for similar sequences.
Cf. A081603 (log_2), A117942 (signed), A117944.
Sequence in context: A133098 A145788 A323861 * A117942 A290092 A066877
KEYWORD
nonn,base
AUTHOR
Paul Barry, Apr 05 2006
EXTENSIONS
a(0) = 1 added to the Name by Bernard Schott, Dec 04 2020
STATUS
approved