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 A132793 Numbers n such that sigma(phi(n))-phi(n) = phi(sigma(n)-n). 2
 3, 70, 138, 792, 924, 1692, 1932, 2124, 2250, 2988, 3852, 30936, 112644, 189252, 240120, 261660, 263928, 338760, 364308, 379470, 390432, 504216, 529110, 785568, 862290, 917700, 979596, 1022310, 1124220, 1404270, 1434072, 2004372, 2526000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Used sigma(n)-n, namely the sum of proper divisors. LINKS Donovan Johnson, Table of n, a(n) for n = 1..100 MAPLE with(numtheory); P:=proc(n) local i, j, k; for i from 1 by 1 to n do j:=sigma(phi(i))-phi(i); k:=phi(sigma(i)-i); if j=k then print(i); fi; od; end: P(150000); MATHEMATICA Select[Range[2600000], DivisorSigma[1, EulerPhi[#]]-EulerPhi[#]==EulerPhi[ DivisorSigma[1, #]-#]&] (* Harvey P. Dale, Mar 24 2016 *) PROG (PARI) isA132793(n)={ if( sigma(eulerphi(n))-eulerphi(n) == eulerphi(sigma(n)-n), 1, 0 ) ; } { for(n=2, 6000000, if(isA132793(n), print(n) ; ) ; ) ; } - R. J. Mathar, Nov 11 2007 CROSSREFS Cf. A000010, A000203, A001229, A018784, A033632, A132794. Sequence in context: A037109 A304146 A305486 * A305086 A316737 A061173 Adjacent sequences:  A132790 A132791 A132792 * A132794 A132795 A132796 KEYWORD nonn AUTHOR Paolo P. Lava and Giorgio Balzarotti, Aug 31 2007 EXTENSIONS More terms from R. J. Mathar, Nov 11 2007 Invalid first term removed by Donovan Johnson, Sep 11 2013 STATUS approved

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Last modified July 3 06:54 EDT 2022. Contains 355031 sequences. (Running on oeis4.)