cp's OEIS Frontend

A374527 Odd numbers whose Collatz trajectory is a Sidon sequence.

%I A374527 #18 Jul 29 2024 06:20:59
%S A374527 1,21,85,151,227,341,1365,5461,14563,21845,87381,349525,932067,
%T A374527 1398101,5592405,22369621,26512143,39768215,59652323,89478485,
%U A374527 357913941,1431655765,3817748707,5726623061
%N A374527 Odd numbers whose Collatz trajectory is a Sidon sequence.
%C A374527 For more information see A375006.
%o A374527 (Python)
%o A374527 from itertools import count, islice
%o A374527 def A374527_gen(startvalue=1): # generator of terms >= startvalue
%o A374527     s = max(startvalue,1)
%o A374527     for n in count(s+(s&1^1),2):
%o A374527         t, a, c = [n], n, set()
%o A374527         while a > 1:
%o A374527             a = 3*a+1 if a&1 else a>>1
%o A374527             for p in t:
%o A374527                 if (b:=p+a) in c:
%o A374527                     break
%o A374527                 c.add(b)
%o A374527             else:
%o A374527                 t.append(a)
%o A374527                 continue
%o A374527             break
%o A374527         else:
%o A374527             yield n
%o A374527 A374527_list = list(islice(A374527_gen(),10)) # _Chai Wah Wu_, Jul 27 2024
%Y A374527 Odd terms of A375006.
%K A374527 nonn,hard,more
%O A374527 1,2
%A A374527 _Markus Sigg_ and _Hugo Pfoertner_, Jul 27 2024
%E A374527 a(23)-a(24) from _Chai Wah Wu_, Jul 29 2024