A275532 - OEIS

%I #7 Sep 08 2022 08:46:17

%S 1,3,7,15,31,36,46,49,55,63,66,67,91,106,119,127,139,145,148,186,190,

%T 197,214,235,248,255,259,274,281,288,301,302,316,325,330,339,346,357,

%U 386,393,399,413,427,442,452,465,497,498,500,505,509,511,519,535,540,557

%N Possible values for sum of numbers in Collatz trajectory (A033493), sorted into ascending order.

%C Values a(n) such that a(n) = A033493(x) = A033493(y)  for distinct numbers x and y: 442, 609, 633, 724, 904, 925, ...

%t Take[#, 56] &@ Union@ Table[Total@ FixedPointList[Which[# == 1, 1, OddQ@ #, 3 # + 1, True, #/2] &, n] - 1, {n, 10^3}] (* _Michael De Vlieger_, Aug 02 2016 *)

%o (Magma) Set(Sort([&+[k eq 1 select n else IsOdd(Self(k-1)) and not IsOne(Self(k-1)) select 3*Self(k-1)+1 else Self(k-1) div 2: k in [1..5*n]]: n in [1..2^10] | &+[k eq 1 select n else IsOdd(Self(k-1)) and not IsOne(Self(k-1)) select 3*Self(k-1)+1 else Self(k-1) div 2: k in [1..5*n]] le 2^10]))

%Y Cf. A033493, A275531.

%K nonn

%O 1,2

%A _Jaroslav Krizek_, Jul 31 2016