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A101335 Let n = d_1 d_2 ... d_k in base 10 and f(n) = Sum_{i=1..k} d_i^k; sequence gives numbers n such that n != f(n) but n = f(f(n)). 1

%I

%S 136,244,2178,6514,58618,76438,2755907,6586433,8139850,9057586,

%T 277668893,756738746,21914086555935085,37878721692554416,

%U 187864919457180831,375609204308055082,13397885590701080090,40091536165423401387,108493282045082839040458,183144838903847612823687

%N Let n = d_1 d_2 ... d_k in base 10 and f(n) = Sum_{i=1..k} d_i^k; sequence gives numbers n such that n != f(n) but n = f(f(n)).

%D Ken Follett, Code to Zero, Dutton, NY 2000, p. 84.

%H Tim Johannes Ohrtmann, <a href="/A101335/b101335.txt">Table of n, a(n) for n = 1..32</a>

%e 136 => 1^3+3^3+6^3=244 => 2^3+4^3+4^3=136.

%e 2178 => 2^4+1^4+7^4+8^4=6514 => 6^4+5^4+1^4+4^4=2178.

%t f[n_] := Plus @@ (IntegerDigits[n]^Floor[Log[10, n] + 1]); Do[ lst = NestList[f, n, 2]; If[lst[[1]] == lst[[3]] != lst[[2]], Print[n]], {n, 110000000}] (* _Robert G. Wilson v_, May 21 2005 *)

%Y Cf. A005188.

%Y Subsequence of A157714.

%K nonn,base,fini

%O 1,1

%A Allyson A. Wilson (Foxtail(AT)southwind.net), May 04 2005

%E a(11)-a(20) from _Tim Johannes Ohrtmann_, Aug 27 2015

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Last modified April 6 21:24 EDT 2020. Contains 333286 sequences. (Running on oeis4.)