login
This site is supported by donations to The OEIS Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A175106 a(0)=1. a(2n-1) = smallest prime > a(2n-2). a(2n) = smallest proper prime power > a(2n-1). 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 (list; graph; refs; listen; history; text; internal format)
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: A060773 A222044 A288937 * 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 16 23:44 EST 2019. Contains 319206 sequences. (Running on oeis4.)