A132140 Numbers containing no zeros in ternary representation and with an initial 1.

1, 4, 5, 13, 14, 16, 17, 40, 41, 43, 44, 49, 50, 52, 53, 121, 122, 124, 125, 130, 131, 133, 134, 148, 149, 151, 152, 157, 158, 160, 161, 364, 365, 367, 368, 373, 374, 376, 377, 391, 392, 394, 395, 400, 401, 403, 404, 445, 446, 448, 449, 454, 455, 457, 458, 472

Offset

1,2

Comments

Intersection of A032924 and A132141;

A132138(A132139(a(n))) = 1.

Links

R. Zumkeller, Table of n, a(n) for n = 1..10000

Index entries for 3-automatic sequences.

Example

14 is in the sequence because its ternary representation is 112;
15 is not in the sequence because its ternary representation is 120.

Maple

a:=proc(n) local nn, L: nn:=convert(n, base, 3): L:=nops(nn): if nn[L]=1 and 0 < product(nn[j], j=1..L) then n else end if end proc: seq(a(n), n=1..500); # Emeric Deutsch, Sep 09 2007

Mathematica

Flatten[Table[FromDigits[Join[{1}, #], 3]&/@Tuples[{1, 2}, n], {n, 0, 5}]] (* Harvey P. Dale, Jan 28 2015 *)

Prog

(Haskell)
a132140 n = a132140_list !! (n-1)
a132140_list = filter f [1..] where
   f x = x < 3 && x == 1 || t > 0 && f x' where (x', t) = divMod x 3
-- Reinhard Zumkeller, Feb 06 2015

Crossrefs

Cf. A032924, A132141, A132138, A132139, A007089.

Sequence in context: A003969 A326828 A348398 * A102703 A283483 A288755

Adjacent sequences: A132137 A132138 A132139 * A132141 A132142 A132143

Keyword

nonn,base,easy

Author

Reinhard Zumkeller, Aug 20 2007

Status

approved