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 A105998 Semiprime function n -> A001358(n) applied four times to n. 5
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS 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

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Last modified January 25 01:49 EST 2020. Contains 331229 sequences. (Running on oeis4.)