|
| |
|
|
A178323
|
|
Numbers n such that phi(reversal(n)) + sigma(reversal(n)) = n.
|
|
0
|
| |
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
If n is in the sequence A070272 then reversal(n) is in this sequence. 10 divides all other terms of the sequence. 2014080 is the only known such term.
If p=6*10^n-1 is a prime greater than 5 then reversal(5*p) is in the sequence, see comment lines of A070272.
There is no further term up to 10^9.
10^12 < a(10) <= 1442827967760. - Giovanni Resta, Sep 04 2018
|
|
|
LINKS
|
Table of n, a(n) for n=1..9.
|
|
|
EXAMPLE
|
2014080 = phi(804102) + sigma(804102), so 2014080 is in the sequence.
|
|
|
MATHEMATICA
|
r[n_]:=FromDigits[Reverse[IntegerDigits[n]]];
Do[If[EulerPhi[r[n]]+DivisorSigma[1, r[n]]==n, Print[n]], {n, 1000000000}]
|
|
|
CROSSREFS
|
Cf. A000010, A000203, A004086, A070272, A178324, A178325.
Sequence in context: A251384 A076465 A144956 * A049361 A252633 A175989
Adjacent sequences: A178320 A178321 A178322 * A178324 A178325 A178326
|
|
|
KEYWORD
|
nonn,base,more
|
|
|
AUTHOR
|
Farideh Firoozbakht, May 28 2010
|
|
|
EXTENSIONS
|
a(9) from Giovanni Resta, Sep 04 2018
|
|
|
STATUS
|
approved
|
| |
|
|
