

A117968


Negative part of inverse of A117966; write n in balanced ternary and then replace (1)'s with 2's.


18



2, 7, 6, 8, 22, 21, 23, 19, 18, 20, 25, 24, 26, 67, 66, 68, 64, 63, 65, 70, 69, 71, 58, 57, 59, 55, 54, 56, 61, 60, 62, 76, 75, 77, 73, 72, 74, 79, 78, 80, 202, 201, 203, 199, 198, 200, 205, 204, 206, 193, 192, 194, 190, 189, 191, 196, 195, 197, 211, 210, 212, 208, 207
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


REFERENCES

D. E. Knuth, The Art of Computer Programming. AddisonWesley, Reading, MA, Vol. 2, pp. 173175


LINKS

Indranil Ghosh, Table of n, a(n) for n = 1..6561
Ken Levasseur, The Balanced Ternary Number System [Broken link]


FORMULA

a(1) = 2, a(3n) = 3a(n), a(3n+1) = 3a(n)+2, a(3n1) = 3a(n)+1.


EXAMPLE

7 in balanced ternary is (1)1(1), changing to 212 ternary is 23, so a(7)=23.


PROG

(Python)
def a(n):
if n==1: return 2
if n%3==0: return 3*a(n/3)
elif n%3==1: return 3*a((n  1)/3) + 2
else: return 3*a((n + 1)/3) + 1
print [a(n) for n in xrange(1, 101)] # Indranil Ghosh, Jun 06 2017


CROSSREFS

Cf. A117966. a(n) = A004488(A117967(n)). Bisection of A140263. A140268 gives the same sequence in ternary.
Sequence in context: A156591 A233770 A138283 * A217568 A320871 A154200
Adjacent sequences: A117965 A117966 A117967 * A117969 A117970 A117971


KEYWORD

base,nonn


AUTHOR

Franklin T. AdamsWatters, Apr 05 2006


STATUS

approved



