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 A114528 Let S(n)=sigma(|n|)-3*n; sequence gives numbers n such that S(S(S(S(n))))=n. May be called {3,1}-Sociable number of orders 1 or 2 or 4. 2

%I #13 Apr 19 2016 01:16:08

%S 1248,1596,28272,30240,32760,463296,678032,1906128,2178540,4694328,

%T 4697616,4698072,11110976,12865770,23569920,30998250,31235904,

%U 37501072,45532800,63723600,76980288,95801088,142990848,146078592,163032720,614533696,1044244800,1379454720

%N Let S(n)=sigma(|n|)-3*n; sequence gives numbers n such that S(S(S(S(n))))=n. May be called {3,1}-Sociable number of orders 1 or 2 or 4.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SociableNumbers.html">Sociable Numbers</a>

%o (PARI) S(n)=sigma(abs(n))-3*n

%o is(n)=S(S(S(S(n))))==n \\ _Charles R Greathouse IV_, Jan 16 2012

%Y Cf. A113285, A114529. Contains A069146 as a subsequence.

%K nonn

%O 1,1

%A _Yasutoshi Kohmoto_, Feb 15 2006

%E a(5)-a(12) from _Charles R Greathouse IV_, Jan 20 2010

%E a(13)-a(28) from _Donovan Johnson_, Jan 16 2012

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Last modified August 13 16:51 EDT 2024. Contains 375144 sequences. (Running on oeis4.)