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 A228871 Odd numbers producing 3 out-of-order odd numbers in the Collatz (3x+1) iteration. 2

%I

%S 3,227,14563,932067,59652323,3817748707,244335917283,15637498706147,

%T 1000799917193443,64051194700380387,4099276460824344803,

%U 262353693492758067427,16790636383536516315363,1074600728546337044183267,68774446626965570827729123

%N Odd numbers producing 3 out-of-order odd numbers in the Collatz (3x+1) iteration.

%C Sequence A198584 gives the first term of the Collatz sequence having exactly 3 odd numbers. This sequence is the subset of A198584 for which the second odd number is larger than the first. The second odd number is (2^(6*n - 2) - 1)/3, which always occurs as the third term of the sequence.

%e The number 3 has the Collatz iteration {3, 10, 5, 16, 8, 4, 2, 1}, which has three out-of-order odd numbers {3, 5, 1}.

%t Table[(2*(2^(6*n - 2) - 1)/3 - 1)/3, {n, 15}]

%o (PARI) a(n)=4^(3*n-1)\3*2\3 \\ _Charles R Greathouse IV_, Mar 11 2017

%Y Cf. A198584 (Collatz iterations having 3 odd numbers).

%Y Cf. A228872 (Collatz iterations producing 3 in-order odd numbers).

%K nonn,easy

%O 1,1

%A _T. D. Noe_, Sep 12 2013

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Last modified July 24 03:29 EDT 2021. Contains 346273 sequences. (Running on oeis4.)