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A132793
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Numbers n such that sigma(phi(n))-phi(n) = phi(sigma(n)-n).
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2
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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
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OFFSET
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1,1
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COMMENTS
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Used sigma(n)-n, namely the sum of proper divisors.
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LINKS
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MAPLE
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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);
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MATHEMATICA
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Select[Range[2600000], DivisorSigma[1, EulerPhi[#]]-EulerPhi[#]==EulerPhi[ DivisorSigma[1, #]-#]&] (* Harvey P. Dale, Mar 24 2016 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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