A105998 Semiprime function n -> A001358(n) applied four times to n.

77, 119, 219, 235, 377, 381, 566, 634, 721, 779, 998, 1006, 1126, 1282, 1294, 1563, 1642, 1745, 1853, 1959, 1961, 2209, 2402, 2483, 2554, 2785, 3005, 3149, 3173, 3242, 3481, 3574, 3587, 3622, 4101, 4282, 4471, 4681, 4714, 4798, 4859, 4882, 5095, 5201

Offset

1,1

Links

Table of n, a(n) for n=1..44.

Formula

a(n) = A001358(A001358(A001358(A001358(n)))).

Example

a(1) = semiprime(semiprime(semiprime(semiprime(1)))) = semiprime(semiprime(semiprime(4))) = semiprime(semiprime(10)) = semiprime(26) = 77.

Mathematica

f[n_] := Plus @@ Flatten[ Table[ # [[2]], {1}] & /@ FactorInteger[ n]]; t = Select[ Range[ 5210], f[ # ] == 2 &]; Table[ Nest[ t[[ # ]] &, n, 4], {n, 45}] (* Robert G. Wilson v, Apr 30 2005 *)

Crossrefs

Cf. A001358, A007097, A091022, A105997, A105999.

Sequence in context: A229826 A330103 A176278 * A039444 A118611 A072431

Adjacent sequences: A105995 A105996 A105997 * A105999 A106000 A106001

Keyword

easy,nonn

Author

Jonathan Vos Post, Apr 29 2005

Extensions

More terms from Robert G. Wilson v, Apr 30 2005

Status

approved