A371052 Numbers whose ternary representation consists of a run of 2's, then a run of 1's, then a run of 0's.

21, 63, 66, 75, 189, 198, 201, 225, 228, 237, 567, 594, 603, 606, 675, 684, 687, 711, 714, 723, 1701, 1782, 1809, 1818, 1821, 2025, 2052, 2061, 2064, 2133, 2142, 2145, 2169, 2172, 2181, 5103, 5346, 5427, 5454, 5463, 5466

Offset

1,1

Comments

All the numbers are multiples of 3.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

The ternary representations of 21, 63, 66 are 210, 2100, 2110.

Maple

seq(seq(seq((2*(3^d-3^(d-a))+3^(d-a)-3^(d-a-b))/2, b=1..d-1-a), a=1..d-2), d=3..10); # Robert Israel, Mar 21 2024

Mathematica

Map[#[[1]] &, Select[Map[{#, Map[#[[1]] &, Split[IntegerDigits[#, 3]]] == {2, 1, 0}} &,
Range[0, 6000, 3]], #[[2]] &]] (* this sequence *)
ToExpression[Map[IntegerString[#, 3] &, %]]   (* A371053 *)
(* Peter J. C. Moses, Mar 06 2024 *)

Prog

(Python)
from itertools import count, islice
def A371052_gen(): # generator of terms
    return ((3**b*(3**a-1)+(3**b-1>>1))*3**(l-a-b) for l in count(3) for a in range(1, l-1) for b in range(1, l-a))
A371052_list = list(islice(A371052_gen(), 20)) # Chai Wah Wu, Mar 21 2024

Crossrefs

Cf. A007089, A008585, A371053.

Sequence in context: A058100 A219856 A371112 * A195106 A143203 A082060

Adjacent sequences: A371049 A371050 A371051 * A371053 A371054 A371055

Keyword

nonn,base,look

Author

Clark Kimberling, Mar 17 2024

Status

approved