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Smallest prime whose reversal is an n-th power.
1

%I #6 May 22 2019 05:45:37

%S 2,61,521,61,23,61277761,821,61277761,23888027348153,4201,

%T 33670369817243,61277761,5265674839116110941,441435249928911950281,

%U 23888027348153,1232787935486158110509626783,270131

%N Smallest prime whose reversal is an n-th power.

%H Robert Israel, <a href="/A059004/b059004.txt">Table of n, a(n) for n = 1..271</a>

%p revdigs:= proc(n) local L,k;

%p L:= convert(n,base,10);

%p add(L[-k]*10^(k-1),k=1..nops(L))

%p end proc:

%p f:= proc(n) local d, k, wmin, v,w;

%p wmin:= infinity;

%p for d from 1 do

%p for k from ceil(10^(d/n)) do

%p v:= k^n;

%p if v >= 10^(d+1) then break fi;

%p w:= revdigs(v);

%p if isprime(w) and w < wmin then wmin:= w fi;

%p od;

%p if wmin < infinity then return wmin fi

%p od

%p end proc:

%p map(f, [$1..20]); # _Robert Israel_, May 22 2019

%t Do[ k = 1; While[ r = ToExpression[ StringReverse[ ToString[ k^n ] ] ]; ! PrimeQ[ r ], k++ ]; Print[ r ], {n, 1, 25} ]

%Y Cf. A007488.

%K nonn,base

%O 1,1

%A _Robert G. Wilson v_, Jan 16 2001