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Search: id:A132793
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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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+0
2
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| 1, 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; listen)
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OFFSET
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1,2
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COMMENT
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Used sigma(n)-n, namely the sum of proper divisors.
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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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PROGRAM
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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 (mathar(AT)strw.leidenuniv.nl), Nov 11 2007
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CROSSREFS
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Cf. A000010, A000203, A001229, A018784, A033632, A132794.
Sequence in context: A012096 A012074 A037109 this_sequence A061173 A156598 A082942
Adjacent sequences: A132790 A132791 A132792 this_sequence A132794 A132795 A132796
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KEYWORD
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nonn
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AUTHOR
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Paolo P. Lava & Giorgio Balzarotti (ppl(AT)spl.at), Aug 31 2007
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 11 2007
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