

A237521


Numbers n such that phi(n) + sigma(n) = reversal(n) + 2.


4




OFFSET

1,1


COMMENTS

a(5), if it exists, is larger than 10^13.
Up to 10^13 the equation phi(n) + sigma(n) = reversal(n)  2 is satisfied only by n = 26330276.


LINKS

Table of n, a(n) for n=1..4.


EXAMPLE

22605 is in the sequence because phi(22605) = 10880, sigma(22605) = 39744, and 10880 + 39744 = 50622 + 2, where 50622 is the reversal of 22605.


MATHEMATICA

Select[Range[493*10^6], EulerPhi[#]+DivisorSigma[1, #]== IntegerReverse[ #]+2&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 01 2020 *)


CROSSREFS

Cf. A070272, A230004, A230005, A230006, A230019, A136544, A237522.
Sequence in context: A290741 A261362 A132942 * A131558 A133857 A232869
Adjacent sequences: A237518 A237519 A237520 * A237522 A237523 A237524


KEYWORD

nonn,base,more


AUTHOR

Giovanni Resta, Feb 08 2014


STATUS

approved



