A129450 a(n) = smallest perfect power that begins and ends with digit n, 1 <= n <= 9; one-digit numbers are excluded.

121, 21952, 343, 484, 5625, 676, 79507, 8242408, 9409

Offset: 1

Author

J. M. Bergot, Apr 12 2007

Keywords

• nonn
• base
• fini
• full

Examples

			a(8) = 202^3 = 8242408; there is no smaller perfect power that begins and ends with digit 8.
		

Crossrefs

Cf. A001597 (perfect powers), A075786 (palindromic perfect powers), A128827.

Programs

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

Extensions

Edited, corrected and extended by Klaus Brockhaus, Apr 16 2007