|
Search: id:A155878
|
|
|
| A155878 |
|
Smallest positive composite number such that a(n)+n is also composite and such that a(n)<a(n+1) |
|
+0
1
|
|
| 4, 8, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 26, 27, 28, 30, 32, 33, 34, 35, 36, 39, 40, 42, 44, 45, 46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 62, 63, 64, 65, 66, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 84, 86, 87, 88, 90, 91, 93, 94, 95, 96, 98, 99, 102, 104, 105, 106, 108
(list; graph; listen)
|
|
|
OFFSET
|
0,1
|
|
|
COMMENT
|
a(0)=4. Adding a(0) to n=0 gives 4+0=4, which is a composite number; adding a(1) to n=1 gives 8+1=9 which is composite; adding a(2) to n=2 gives 10+2=12 which is composite; adding a(3) to n=3 gives 12+3=15 which is composite; etc.
|
|
MAPLE
|
isA002808 := proc(n) option remember; RETURN(n>= 4 and not isprime(n)) ; end: A155878:= proc(n) option remember; local a; if n = 0 then 4; else for a from procname(n-1)+1 do if isA002808(a) and isA002808(a+n) then RETURN(a) ; fi; od: fi; end: seq(A155878(n), n=0..100) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 31 2009]
|
|
CROSSREFS
|
A155874
Sequence in context: A108806 A074776 A153762 this_sequence A029886 A102218 A057166
Adjacent sequences: A155875 A155876 A155877 this_sequence A155879 A155880 A155881
|
|
KEYWORD
|
base,easy,nonn
|
|
AUTHOR
|
Eric Angelini (eric.angelini(AT)skynet.be), Jan 29 2009
|
|
EXTENSIONS
|
Extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 31 2009
|
|
|
Search completed in 0.002 seconds
|
