A023693 Numbers with exactly 2 1's in ternary expansion.

4, 10, 12, 14, 16, 22, 28, 30, 32, 34, 36, 38, 42, 44, 46, 48, 50, 52, 58, 64, 66, 68, 70, 76, 82, 84, 86, 88, 90, 92, 96, 98, 100, 102, 104, 106, 108, 110, 114, 116, 126, 128, 132, 134, 136, 138, 140, 142, 144, 146, 150, 152, 154, 156, 158, 160, 166, 172, 174

Offset

1,1

Comments

From Bernard Schott, Jun 19 2023: (Start)

A003946 \ {1} is a subsequence since for m = 4*3^(k-1) with k >= 1, ternary expansion of m is 110...0 with (k-1) trailing 0's.

A034472 \ {2} is a subsequence since for m = 3^k + 1 with k >= 1, ternary expansion of m is 10...01 with (k-1) 0's between first and last 1's. (End)

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

30 is a term since 30 = 1010_3 with exactly 2 1's.

Mathematica

Select[ Range[ 162 ], (Count[ IntegerDigits[ #, 3 ], 1 ]==2)& ]

Prog

(PARI) isok(k) = #select(x->(x==1), digits(k, 3)) == 2; \\ Michel Marcus, Jun 19 2023

Crossrefs

Cf. A003946, A007089, A034472.

Sequence in context: A102998 A071179 A155475 * A299634 A181053 A239055

Adjacent sequences: A023690 A023691 A023692 * A023694 A023695 A023696

Keyword

nonn,base,easy

Author

Olivier Gérard

Status

approved