|
| |
|
|
A155090
|
|
Composites n without even prime factor in composite(n).
|
|
0
| |
|
|
4, 8, 12, 15, 21, 26, 30, 33, 35, 38, 40, 44, 46, 49, 55, 58, 63, 66, 68, 70, 77, 81, 84, 86, 88, 90, 92, 94, 100, 102, 106, 108, 110, 112, 116, 118, 121, 123, 126, 129, 134, 136, 140, 142, 144, 146, 150, 154, 156, 158, 160, 162, 165, 169, 171, 176, 180, 183, 185
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
EXAMPLE
| If n=4=composite and 3*3=9=composite(4), then 4=a(1). If n=8=composite and 3*5=15=composite(8), then 8=a(2). If n=12=composite and 3*7=21=composite(12), then=a(3), etc.
|
|
|
MAPLE
| Contribution from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 10 2010: (Start)
A002808 := proc(n) option remember ; 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:
isA002808 := proc(n) n >= 4 and not isprime(n) ; end proc:
for i from 1 to 400 do if isA002808(i) then c := A002808(i) ; if type(c, 'odd') then printf("%d, ", i) ; end if; end if; end do: (End)
|
|
|
CROSSREFS
| Cf. A002808.
Sequence in context: A188069 A190697 A190687 * A081747 A020647 A196032
Adjacent sequences: A155087 A155088 A155089 * A155091 A155092 A155093
|
|
|
KEYWORD
| nonn,base
|
|
|
AUTHOR
| Juri-Stepan Gerasimov (2stepan(AT0rambler.ru), Jan 20 2009
|
|
|
EXTENSIONS
| Entries checked by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 10 2010
|
| |
|
|
