|
Search: id:A089090
|
|
|
| A089090 |
|
a(n) is the smallest composite number coprime to n. |
|
+0
1
|
|
| 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 49, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 49, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 25, 4, 9, 4, 9, 4, 49, 4, 9, 4, 9, 4, 25, 4
(list; graph; listen)
|
|
|
OFFSET
|
0,1
|
|
|
FORMULA
|
a[n]=A053669[n]^2
|
|
EXAMPLE
|
n=30: below 30 coprimes to 30 phi[30]=8 numbers are relevant but each 1 or primes; so a[n]>30; the first suitable number is a[30]=49; If n is the n-th primorial, then a[n]=p(n+1)^2.
|
|
MATHEMATICA
|
m=0; Table[fla=1; Do[s=GCD[n, k]; If[Equal[s, 1]&&!PrimeQ[n]&&!Equal[n, 1]&& Equal[fla, 1], m=m+1; Print[n]; fla=0], {n, 1, 130}], {k, 1, 256}]
|
|
CROSSREFS
|
Cf. A053669, A007978, A053670-A053674, A090091-A090093.
Sequence in context: A141653 A071793 A010714 this_sequence A113484 A061767 A131016
Adjacent sequences: A089087 A089088 A089089 this_sequence A089091 A089092 A089093
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Labos E. (labos(AT)ana.sote.hu), Nov 26 2003
|
|
|
Search completed in 0.002 seconds
|
