A105997 Semiprime function n -> A001358(n) applied three times to n.

26, 39, 74, 77, 118, 119, 178, 194, 219, 235, 299, 301, 329, 377, 381, 454, 471, 502, 535, 565, 566, 634, 679, 703, 721, 779, 842, 886, 893, 914, 973, 995, 998, 1006, 1126, 1174, 1227, 1282, 1294, 1317, 1337, 1343, 1389, 1418, 1457, 1563, 1577, 1623, 1642

Offset

1,1

Links

Table of n, a(n) for n=1..49.

Formula

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

Example

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

Mathematica

f[n_] := Plus @@ Flatten[ Table[ # [[2]], {1}] & /@ FactorInteger[ n]]; t = Select[ Range[ 1700], f[ # ] == 2 &]; Table[ Nest[ t[[ # ]] &, n, 3], {n, 50}] (* Robert G. Wilson v, Apr 30 2005 *)

Crossrefs

Cf. A001358, A007097, A091022, A105998, A105999.

Sequence in context: A043927 A330701 A050702 * A354345 A075288 A320255

Adjacent sequences: A105994 A105995 A105996 * A105998 A105999 A106000

Keyword

easy,nonn

Author

Jonathan Vos Post, Apr 29 2005

Extensions

Corrected and extended by Robert G. Wilson v, Apr 30 2005

Status

approved