

A230005


Numbers n such that phi(n) + sigma(n) = reversal(n)  4.


6



489, 4629, 296206, 460029, 29589106, 46000029, 2927272726, 4045046518, 21223345084, 29600331295, 296151515206, 460000000029
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

If p = 15*10^k+10+(10^k1)/3 is prime then 3*p is in the sequence.
a(7) is greater than 1.3*10^8.
a(11) > 10^11.  Donovan Johnson, Nov 08 2013
If p=(1/11)*(23*100^m1) is prime then 14*p is a term of the sequence.  Farideh Firoozbakht, Nov 08 2013
a(13) > 10^13.  Giovanni Resta, Feb 08 2014
If p = (1685*10^(2k+2)+31)/33 is prime then 58*p is in the sequence. For k = 0, 3, 9, 30, 42, 51, 120, 846, ... p is prime.  Farideh Firoozbakht, Feb 10 2014


LINKS

Table of n, a(n) for n=1..12.


EXAMPLE

489 is in the sequence because phi(489)+sigma(489) = 324+656 = 9844 = reversal(489)4.


MATHEMATICA

Do[If[FromDigits@Reverse@IntegerDigits@n4 == EulerPhi[n] + DivisorSigma[1, n], Print[n]], {n, 130000000}]


PROG

(PARI) is(n)=subst(Polrev(digits(n)), 'x, 10)4==eulerphi(n)+sigma(n) \\ Charles R Greathouse IV, Nov 08 2013


CROSSREFS

Cf. A000010, A000203, A004086, A070272, A230004, A230006, A230019, A136544, A237521, A237522.
Sequence in context: A201215 A214807 A251676 * A221940 A221739 A068751
Adjacent sequences: A230002 A230003 A230004 * A230006 A230007 A230008


KEYWORD

nonn,base,more


AUTHOR

Farideh Firoozbakht, Nov 07 2013


EXTENSIONS

a(7)a(10) from Donovan Johnson, Nov 08 2013
a(11)a(12) from Giovanni Resta, Feb 06 2014


STATUS

approved



