|
Search: id:A114930
|
|
|
| A114930 |
|
Numbers n such that phi(n)=2*reversal(n). |
|
+0
2
|
| |
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
If m>1 and p=3*10^m+7 is prime then 90*p is in the sequence because phi(90*p)=phi(90)*phi(p)=24*(3*10^m+6)=2*(36*10^m+72) =2*reversal(27*10^m+63)=2*reversal(9*p)=2*reversal(90*p). Note that 30 divides all known terms of this sequence. Next term is greater than 11*10^7.
|
|
EXAMPLE
|
637062480 is in the sequence because phi(637062480)=2*84260736=
2*reversal(637062480).
|
|
MATHEMATICA
|
Do[If[EulerPhi[n]==2*FromDigits[Reverse[IntegerDigits[n]]], Print[n]], {n, 110000000}]
|
|
CROSSREFS
|
Cf. A069215, A114931.
Sequence in context: A033288 A057880 A151967 this_sequence A068757 A031836 A094494
Adjacent sequences: A114927 A114928 A114929 this_sequence A114931 A114932 A114933
|
|
KEYWORD
|
base,more,nonn
|
|
AUTHOR
|
Farideh Firoozbakht (mymontain(AT)yahoo.com), Jan 29 2006
|
|
|
Search completed in 0.002 seconds
|
