A050439 Fifth-order composites.

39, 49, 55, 56, 60, 69, 74, 77, 78, 84, 93, 94, 95, 100, 105, 106, 110, 115, 119, 124, 125, 126, 130, 133, 140, 141, 145, 152, 155, 156, 159, 162, 164, 165, 170, 174, 180, 183, 184, 188, 189, 198, 201, 202, 203, 206, 207, 209, 212, 213, 218, 222, 225, 231

Offset

1,1

Links

Table of n, a(n) for n=1..54.

N. Fernandez, An order of primeness, F(p)

N. Fernandez, An order of primeness [cached copy, included with permission of the author]

Formula

Let C(n) be the n-th composite number, with C(1)=4. Then these are numbers C(C(C(C(C(n))))).

Example

C(C(C(C(C(8))))) = C(C(C(C(15)))) = C(C(C(25))) = C(C(38)) = C(55) = 77. So 77 is in the sequence.

Maple

C := remove(isprime, [$4..1000]): seq(C[C[C[C[C[n]]]]], n=1..100);

Crossrefs

Cf. A049076-A049081, A006450, A050435, A050436, A050438, A050440.

Sequence in context: A143746 A064399 A235151 * A199993 A181488 A020305

Adjacent sequences: A050436 A050437 A050438 * A050440 A050441 A050442

Keyword

easy,nonn

Author

Michael Lugo (mlugo(AT)thelabelguy.com), Dec 22 1999

Extensions

More terms from Asher Auel Dec 15 2000

Status

approved