A206034 a(n) is the last defined element in the sequence n, f(n), f(f(n)), ..., where f(t) = lcm(t,(b+c)/2) with b < c smallest consecutive divisors of t with c - b > 1 and f(t) is undefined if such b, c do not exist or b + c is odd.

1, 2, 6, 360360, 360360, 6, 420, 360360, 18, 10, 66, 360360, 5460, 14, 360360, 2329089562800, 306, 18, 190, 360360, 42, 22, 8288280, 360360, 1801800, 26, 54, 420, 10450440, 360360, 52573842877942565273243107104095419458814459401768000

Offset

1,2

Comments

a(256) = 996169...200000 has 3547 decimal digits. - Alois P. Heinz, Mar 12 2012

Links

Alois P. Heinz, Table of n, a(n) for n = 1..255

Example

a(4) = 360360 because the sequence is 4, 12, 60, 120, 840, 2520, 27720, 360360, but 360360 has b=15 and c=18 and f(360360) is not defined.

Crossrefs

Sequence in context: A165710 A151995 A152210 * A299376 A364750 A167446

Adjacent sequences: A206031 A206032 A206033 * A206035 A206036 A206037

Keyword

nonn

Author

J. Lowell, Mar 12 2012

Extensions

More terms from Alois P. Heinz, Mar 12 2012

Status

approved