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 A247080 Numbers whose Euler totient is the reverse of the sum of its aliquot parts. 1
 2, 735, 7665, 11505, 42630, 64578, 3440409, 11263073973 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Value of x such that phi(x) = Rev(sigma(x) - x). a(9) > 2*10^11. - Hiroaki Yamanouchi, Nov 22 2014 a(9) > 10^13. - Giovanni Resta, Aug 26 2019 LINKS EXAMPLE phi(2) = 1 and sigma(2) - 2 = 1. phi(735) = 336 and sigma(735) - 735 = 633. phi(7665) = 3456 and sigma(7665) - 7665 = 6543. MAPLE with(numtheory): T:=proc(w) local x, y, z; x:=w; y:=0; for z from 1 to ilog10(x)+1 do y:=10*y+(x mod 10); x:=trunc(x/10); od; y; end: P:=proc(q) local n; for n from 1 to q do if phi(n)=T(sigma(n)-n) then print(n); fi; od; end: P(10^9); MATHEMATICA Select[Range[10^6], EulerPhi[#] == FromDigits[Reverse[IntegerDigits[DivisorSigma[1, #] - #]]] &] (* Michael De Vlieger, Jan 29 2015 *) PROG (PARI) rev(n) = subst(Polrev(digits(n)), x, 10); isok(n) = rev(sigma(n)-n) == eulerphi(n); \\ Michel Marcus, Jan 29 2015 CROSSREFS Cf. A000010, A001065, A069225, A254320. Sequence in context: A109949 A151591 A252986 * A145124 A102969 A179960 Adjacent sequences:  A247077 A247078 A247079 * A247081 A247082 A247083 KEYWORD nonn,base,more AUTHOR Paolo P. Lava, Nov 17 2014 EXTENSIONS a(7)-a(8) from Hiroaki Yamanouchi, Nov 22 2014 STATUS approved

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Last modified August 11 15:12 EDT 2020. Contains 336428 sequences. (Running on oeis4.)