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%I #7 Sep 08 2022 08:45:30
%S 121,21952,343,484,5625,676,79507,8242408,9409
%N a(n) = smallest perfect power that begins and ends with digit n, 1 <= n <= 9; one-digit numbers are excluded.
%e a(8) = 202^3 = 8242408; there is no smaller perfect power that begins and ends with digit 8.
%o (Magma) PP:=[1] cat [ n: n in [2..9000000] | IsPower(n) ]; firstlast:=function(x); for n:=1 to #PP do k:=Intseq(PP[n], 10); if #k gt 1 and k[1] eq x and k[ #k] eq x then return PP[n]; end if; end for; return -1; end function; [ firstlast(d): d in [1..9] ]; // _Klaus Brockhaus_, Apr 16 2007
%Y Cf. A001597 (perfect powers), A075786 (palindromic perfect powers), A128827.
%K nonn,base,fini,full
%O 1,1
%A _J. M. Bergot_, Apr 12 2007
%E Edited, corrected and extended by _Klaus Brockhaus_, Apr 16 2007
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