Search: id:A133048
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%I A133048
%S A133048 0,1,2,3,4,5,6,7,8,9,1,1,2,3,4,5,6,7,8,9,2,1,4,9,16,25,36,49,64,81,3,1,
%T A133048 8,27,64,125,216,343,512,729,4,1,16,81,256,625,1296,2401,4096,6561,5,1,
%U A133048 32,243,1024,3125,7776,16807,32768,59049,6,1,64,729,4096,15625,46656,117649
%N A133048 Powerback(n): reverse the decimal expansion of n, drop any leading zeros, 
               then apply the powertrain map of A133500 to the resulting number.
%H A133048 N. J. A. Sloane, <a href="b133048.txt">Table of n, a(n) for n = 0..10000</
               a>
%e A133048 E.g. 240 -> (0)42 -> 4^2 = 16; 12345 -> 54321 -> 5^4*3^2*1 = 5625.
%p A133048 powerback:=proc(n) local a,i,j,t1,t2,t3;
%p A133048 if n = 0 then RETURN(0); fi;
%p A133048 t1:=convert(n, base, 10); t2:=nops(t1);
%p A133048 for i from 1 to t2 do if t1[i] > 0 then break; fi; od:
%p A133048 a:=1; t3:=t2-i+1;
%p A133048 for j from 0 to floor(t3/2)-1 do a := a*t1[i+2*j]^t1[i+2*j+1]; od:
%p A133048 if t3 mod 2 = 1 then a:=a*t1[t2]; fi;
%p A133048 RETURN(a); end;
%Y A133048 Cf. A131571 (fixed points), A133059 and A133134 (records); A133500 (powertrain).
%Y A133048 Cf. A133144 (length of trajectory), A031346 and A003001 (persistence).
%Y A133048 Sequence in context: A004427 A113230 A065881 this_sequence A054055 A067456 
               A052429
%Y A133048 Adjacent sequences: A133045 A133046 A133047 this_sequence A133049 A133050 
               A133051
%K A133048 nonn,base
%O A133048 0,3
%A A133048 J. H. Conway and N. J. A. Sloane (njas(AT)research.att.com), Dec 31 2007

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