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%I #18 Oct 13 2019 23:21:14
%S 55,155,226,244,247,255,262,274,424,427,442,472,505,515,525,550,551,
%T 552,622,724,742,1039,1093,1139,1193,1234,1238,1243,1283,1309,1319,
%U 1324,1328,1342,1382,1390,1391,1423,1432,1823,1832,1903,1913,1930,1931
%N Numbers from which 8 steps are needed to reach a prime under "Sum of digits raised to its digits' powers" procedure.
%C 0^0 is treated as 1. - _Harvey P. Dale_, Mar 06 2013
%H Charles R Greathouse IV, <a href="/A046438/b046438.txt">Table of n, a(n) for n = 1..10000</a>
%t nxt[n_]:=Module[{idn=IntegerDigits[n]/.{0->1}},Total[idn^idn]]; Select[ Range[ 2000],Rest[PrimeQ[NestList[nxt,#,8]]]=={False,False,False,False,False,False,False,True}&] (* _Harvey P. Dale_, Mar 06 2013 *)
%o (PARI) is(n)=for(i=1,8,if(i>1&&isprime(n),return(0));n=digits(n);n= sum(i=1,#n,n[i]^n[i]));isprime(n) \\ _Charles R Greathouse IV_, Mar 06 2013
%Y Cf. A046431.
%K nonn,base
%O 1,1
%A _Patrick De Geest_, Jul 15 1998
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