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A350160
Odd numbers whose Collatz trajectory does not include 5 as a term.
2
1, 21, 75, 85, 113, 151, 201, 227, 267, 301, 341, 401, 403, 423, 453, 475, 535, 537, 605, 633, 635, 713, 715, 803, 805, 847, 891, 909, 951, 953, 955, 1003, 1069, 1073, 1075, 1129, 1131, 1191, 1205, 1267, 1271, 1273, 1337, 1365, 1425, 1427, 1431, 1433, 1505
OFFSET
1,2
COMMENTS
Odd terms of A308149.
After a(2), each term's Collatz trajectory includes 256.
A plot of a(n)/n vs. n has an interesting quasiperiodic form with a decreasing frequency. Does lim_{n->infinity} a(n)/n equal 32?
EXAMPLE
The Collatz trajectories of the first few terms are as follows:
.
n a(n) trajectory
-- ---- ------------------------------------------------------------
1 1 1
2 21 21, 64, 32, 16, 8, 4, 2, 1
3 75 75, 226, 113, 340, 170, 85, 256, 128, 64, 32, 16, 8, 4, 2, 1
4 85 85, 256, 128, 64, 32, 16, 8, 4, 2, 1
5 113 113, 340, 170, 85, 256, 128, 64, 32, 16, 8, 4, 2, 1
MATHEMATICA
Select[Range[1, 1500, 2], !MemberQ[NestWhileList[If[OddQ[#1], 3*#1 + 1, #1/2] &, #, #1 > 1 &], 5] &] (* Amiram Eldar, Dec 18 2021 *)
CROSSREFS
Cf. A308149.
Sequence in context: A109357 A283802 A082041 * A316887 A296155 A218960
KEYWORD
nonn
AUTHOR
Jon E. Schoenfield, Dec 17 2021
STATUS
approved