A155109 - OEIS

A155109

Odd nonprime numbers k such that composite(k) is even.

1, 9, 25, 27, 39, 45, 51, 57, 65, 69, 75, 85, 87, 91, 93, 95, 99, 105, 111, 115, 117, 119, 125, 133, 135, 141, 143, 145, 147, 153, 155, 159, 161, 175, 177, 187, 201, 207, 209, 213, 215, 217, 221, 231, 235, 237, 243, 247, 253, 255, 259, 261, 273, 275, 279, 287

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..56.

MAPLE

isA002808 := proc(n) n >= 4 and not isprime(n) ; end proc:

A002808 := proc(n) option remember ; local a; if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then return a; end if; end do; end if; end proc:

for n from 1 to 400 do if type(n, 'odd') and not isprime(n) then c := A002808(n) ; if type(c, 'even') then printf("%d, ", n) ; end if; end if; end do: # R. J. Mathar, May 10 2010

MATHEMATICA

With[{nn=400}, Select[Flatten[Position[Complement[Range[4, nn], Prime[ Range[PrimePi[nn]]]], _?(EvenQ[#]&)]], OddQ[#]&&!PrimeQ[#]&]] (* Harvey P. Dale, Jun 23 2013 *)

CROSSREFS

Cf. A002808, A141468.

Sequence in context: A304035 A339726 A377702 * A268576 A053850 A225498

Adjacent sequences: A155106 A155107 A155108 * A155110 A155111 A155112

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Jan 20 2009

EXTENSIONS

Edited by N. J. A. Sloane, Jan 30 2009

Corrected (67, 79, 113, 189, 219 removed) by R. J. Mathar, May 10 2010

STATUS

approved