A225105 Odd numbers n such that the largest odd term in Collatz(3x+1) trajectory of n is prime.

3, 5, 7, 9, 11, 13, 15, 17, 19, 23, 25, 29, 35, 37, 39, 53, 59, 61, 67, 75, 79, 87, 89, 99, 101, 105, 113, 115, 119, 131, 149, 153, 157, 173, 179, 181, 187, 197, 211, 219, 229, 241, 247, 249, 255, 267, 269, 277, 281, 307, 317, 329, 349, 371, 373, 383, 397

Offset

1,1

Links

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

Example

15 is in the list since highest odd number in Collatz trajectory of 15 is 53, a prime.

Mathematica

Coll[n_]:=NestWhileList[If[EvenQ[#], #/2, 3*# + 1] &, n, #>1&]; t={}; Do[If[PrimeQ[Max[Select[Coll[n], OddQ]]], AppendTo[t, n]], {n, 1, 300, 2}]; t

Prog

(Haskell)
a225105 n = a225105_list !! (n-1)
a225105_list = filter
   ((== 1) . a010051' . maximum . filter odd . a070165_row) a005408_list
-- Reinhard Zumkeller, Apr 30 2013

Crossrefs

Cf. A087232.

Cf. A010051, A070165, A005408, A220237, A025586.

Sequence in context: A138217 A074775 A356845 * A143451 A352547 A014261

Adjacent sequences: A225102 A225103 A225104 * A225106 A225107 A225108

Keyword

nonn

Author

Jayanta Basu, Apr 28 2013

Status

approved