A176363 Non-semiprime numbers of order 2.

1, 2, 3, 7, 11, 12, 17, 18, 19, 24, 27, 28, 29, 30, 36, 37, 42, 43, 44, 45, 47, 48, 54, 56, 61, 63, 64, 66, 67, 68, 71, 72, 75, 78, 79, 80, 83, 89, 90, 92, 97, 98, 100, 101, 102, 104, 105, 107, 108, 110, 112, 114, 116, 117, 120, 125, 126, 131, 132, 135, 137, 144, 147, 148

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 16 2010

Keywords

• nonn

Comments

Non-semiprimes with non-semiprime subscripts (or indices).

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..10000

Programs

Maple

A100959 := proc(n) option remember; if n = 1 then 1; else for a from procname(n-1)+1 do if numtheory[bigomega](a) <> 2 then return a; end if; end do end if; end proc: A176363 := proc(n) A100959(A100959(n)) ; end proc: seq(A176363(n),n=1..80) ; # R. J. Mathar, Apr 25 2010

Formula

a(n) = A100959(A100959(n)).

Extensions

Corrected (66 inserted) R. J. Mathar, Apr 25 2010