A368949 Complement of A368087 in A174905.

21, 33, 39, 51, 55, 57, 65, 69, 85, 87, 93, 95, 111, 115, 119, 123, 129, 133, 141, 145, 147, 155, 159, 161, 171, 177, 183, 185, 201, 203, 205, 207, 213, 215, 217, 219, 230, 235, 237, 249, 253, 259, 261, 265, 267, 275, 279, 287, 290, 291, 295, 301, 303, 305, 309, 310, 319, 321, 327, 329, 333, 335, 339, 341

Offset

1,1

Comments

A298855 is a subsequence, number 147 = 3 * 7^2 is the first entry in A368949 not in A298855. This sequence is a subsequence of A174905 = A241008 union A241010.

Alternate definition: Every number n in this sequence has at least 2 distinct odd prime factors and its symmetric representation of sigma consists only of parts of width 1.

Links

Table of n, a(n) for n=1..64.

Example

21 is the smallest number in this sequence since 3 * 5 is not in A174905.
The smallest number in this sequence with 3 distinct odd prime factors is 903 = 3*7*43 which has width pattern (A341969) 101010101010101 of length 17 since ... < d_i < 2 * d_i < d_(i+1) < 2 * d_(i+1) ... holds for all its divisors.

Mathematica

(* a174905[ ] is defined in A174905 and propQ[ ] in A368087 *)
a368949[m_, n_] := Select[Range[m, n], a174905[#]&&!propQ[#]&]
a368949[1, 350]

Crossrefs

Cf. A005279, A174905, A235791, A237048, A237270, A237593, A241008, A241010, A249223, A298855, A341969, A368087.

Sequence in context: A181677 A036382 A343454 * A298855 A354813 A273201

Adjacent sequences: A368946 A368947 A368948 * A368950 A368951 A368952

Keyword

nonn

Author

Hartmut F. W. Hoft, Jan 10 2024

Status

approved