A132793 Numbers n such that sigma(phi(n))-phi(n) = phi(sigma(n)-n).

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

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), print1(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