A175106 a(0)=1. a(2n-1) = smallest prime > a(2n-2). a(2n) = smallest proper prime power > a(2n-1).

1, 2, 4, 5, 8, 11, 16, 17, 25, 29, 32, 37, 49, 53, 64, 67, 81, 83, 121, 127, 128, 131, 169, 173, 243, 251, 256, 257, 289, 293, 343, 347, 361, 367, 512, 521, 529, 541, 625, 631, 729, 733, 841, 853, 961, 967, 1024, 1031, 1331, 1361, 1369, 1373, 1681, 1693, 1849

Offset

0,2

Comments

Alternating between elements of A000040 and A025475. - R. J. Mathar, Mar 09 2010

Links

Table of n, a(n) for n=0..54.

Maple

From R. J. Mathar, Mar 09 2010: (Start)
isA025475 := proc(n) pdec := ifactors(n)[2] ; if nops(pdec) = 1 then return ( op(2, op(1, pdec)) > 1 ); else false; end if; end proc:
A175106 := proc(n) option remember; local a; if n = 0 then 1; else if type(n, 'odd') then nextprime(procname(n-1)) ; else for a from procname(n-1)+1 do if isA025475(a) then return a ; end if; end do ; end if; end if; end proc:
seq(A175106(n), n=0..80) ; (End)

Crossrefs

Cf. A246547.

Sequence in context: A288937 A327063 A324926 * A216566 A205728 A074824

Adjacent sequences: A175103 A175104 A175105 * A175107 A175108 A175109

Keyword

nonn

Author

Leroy Quet, Feb 11 2010

Extensions

Extended by Ray Chandler, Mar 11 2010

More terms from R. J. Mathar, Mar 09 2010

Status

approved