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 A166024 Define dsf(n) = A045503(n) = n_1^{n_1}+n_2^{n_2}+n_3^{n_3} + n_m^{n_m}, where {n_1,n_2,n_3,...n_m} is the list of the decimal digits of n. dsf(421845123) = 16780890 and dsf(16780890) = 421845123, so these 2 numbers make a loop for the function dsf. 4
 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890, 421845123, 16780890 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS In fact there are only 8 loops among all the nonnegative integers for the "dsf" function that we defined. Periodic with period 2. LINKS Ryohei Miyadera, Curious Properties of an Iterative Process,Mathsource, Wolfram Library Archive Index entries for linear recurrences with constant coefficients, signature (0, 1). FORMULA a(n+1) = dsf(a(n)). MATHEMATICA dsf[n_] := Block[{m = n, t}, t = IntegerDigits[m]; Sum[Max[1, t[[k]]]^t[[k]], {k, Length[t]}]]; NestList[dsf, 421845123, 4] LinearRecurrence[{0, 1}, {421845123, 16780890}, 24] (* Ray Chandler, Aug 25 2015 *) CROSSREFS Cf. A165942, A045503. Sequence in context: A323537 A186795 A234193 * A234396 A017408 A017528 Adjacent sequences:  A166021 A166022 A166023 * A166025 A166026 A166027 KEYWORD nonn,base,easy AUTHOR Ryohei Miyadera, Satoshi Hashiba and Koichiro Nishimura, Oct 04 2009 EXTENSIONS Comment and editing by Charles R Greathouse IV, Aug 02 2010 STATUS approved

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Last modified July 15 20:00 EDT 2019. Contains 325056 sequences. (Running on oeis4.)