

A228871


Odd numbers producing 3 outoforder odd numbers in the Collatz (3x+1) iteration.


2



3, 227, 14563, 932067, 59652323, 3817748707, 244335917283, 15637498706147, 1000799917193443, 64051194700380387, 4099276460824344803, 262353693492758067427, 16790636383536516315363, 1074600728546337044183267, 68774446626965570827729123
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OFFSET

1,1


COMMENTS

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.


LINKS

Table of n, a(n) for n=1..15.


EXAMPLE

The number 3 has the Collatz iteration {3, 10, 5, 16, 8, 4, 2, 1}, which has three outoforder odd numbers {3, 5, 1}.


MATHEMATICA

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


PROG

(PARI) a(n)=4^(3*n1)\3*2\3 \\ Charles R Greathouse IV, Mar 11 2017


CROSSREFS

Cf. A198584 (Collatz iterations having 3 odd numbers).
Cf. A228872 (Collatz iterations producing 3 inorder odd numbers).
Sequence in context: A241098 A254157 A131493 * A195500 A099426 A332123
Adjacent sequences: A228868 A228869 A228870 * A228872 A228873 A228874


KEYWORD

nonn,easy


AUTHOR

T. D. Noe, Sep 12 2013


STATUS

approved



