A050438 Fourth-order composites.

26, 33, 38, 39, 42, 49, 52, 55, 56, 60, 68, 69, 70, 74, 77, 78, 80, 84, 88, 93, 94, 95, 98, 100, 105, 106, 110, 115, 118, 119, 121, 124, 125, 126, 130, 133, 138, 140, 141, 145, 146, 152, 154, 155, 156, 159, 160, 162, 164, 165, 170, 174, 176, 180, 183, 184

Offset

1,1

Links

Table of n, a(n) for n=1..56.

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(n)))).

Example

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

Maple

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

Crossrefs

Cf. A049076-A049081, A006450, A050435, A050436, A050439, A050440.

Sequence in context: A153224 A177210 A050770 * A047822 A048126 A080932

Adjacent sequences: A050435 A050436 A050437 * A050439 A050440 A050441

Keyword

easy,nonn

Author

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

Extensions

More terms from Asher Auel Dec 15 2000

Status

approved