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A046439
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9 steps needed to reach a prime under "Sum of digits raised to its digits' powers" procedure.
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2
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133, 138, 183, 303, 308, 313, 318, 330, 331, 380, 381, 389, 398, 446, 464, 644, 789, 798, 803, 813, 830, 831, 839, 879, 893, 897, 938, 978, 983, 987, 1005, 1015, 1024, 1042, 1046, 1050, 1051, 1064, 1105, 1115, 1124, 1142, 1146, 1150, 1151, 1164, 1204
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OFFSET
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0,1
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LINKS
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MATHEMATICA
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sop[n_] := Total[#^# & /@ (IntegerDigits[n] /. {0 -> 1})]; Select[Range[1205], (z = Boole /@ PrimeQ[Rest[NestList[sop, #, 9]]])[[9]] - Total[Drop[z, -1]] == 1 &] (* Jayanta Basu, Jun 25 2013 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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