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 A178323 Numbers n such that phi(reversal(n)) + sigma(reversal(n)) = n. 0
 572, 592, 5992, 599992, 2014080, 5999992, 594637872, 599999992, 599999999992 (list; graph; refs; listen; history; text; internal format)
 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 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

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Last modified March 31 07:39 EDT 2023. Contains 361645 sequences. (Running on oeis4.)