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Odd numbers whose Collatz trajectory is a Sidon sequence.
2

%I #18 Jul 29 2024 06:20:59

%S 1,21,85,151,227,341,1365,5461,14563,21845,87381,349525,932067,

%T 1398101,5592405,22369621,26512143,39768215,59652323,89478485,

%U 357913941,1431655765,3817748707,5726623061

%N Odd numbers whose Collatz trajectory is a Sidon sequence.

%C For more information see A375006.

%o (Python)

%o from itertools import count, islice

%o def A374527_gen(startvalue=1): # generator of terms >= startvalue

%o s = max(startvalue,1)

%o for n in count(s+(s&1^1),2):

%o t, a, c = [n], n, set()

%o while a > 1:

%o a = 3*a+1 if a&1 else a>>1

%o for p in t:

%o if (b:=p+a) in c:

%o break

%o c.add(b)

%o else:

%o t.append(a)

%o continue

%o break

%o else:

%o yield n

%o A374527_list = list(islice(A374527_gen(),10)) # _Chai Wah Wu_, Jul 27 2024

%Y Odd terms of A375006.

%K nonn,hard,more

%O 1,2

%A _Markus Sigg_ and _Hugo Pfoertner_, Jul 27 2024

%E a(23)-a(24) from _Chai Wah Wu_, Jul 29 2024