A076442 - OEIS

%I #12 Mar 14 2020 05:55:26

%S 1,9,1331,3375,35937,59319,357911,753571,759375,5177717,5359375,

%T 5735339,9393931,17373979,37595375,39135393,37159393753,99317171591,

%U 175333911173,397551775977,1913551573375,9735913353977,11997979755957,17171515157399,335571975137771

%N Odd-digit perfect powers.

%C a(19) > 1.3*10^11. - _Robert G. Wilson v_, Dec 17 2002

%H Giovanni Resta, <a href="/A076442/b076442.txt">Table of n, a(n) for n = 1..566</a> (terms < 10^57)

%t NextOddNbr[n_] := Block[{d = If[ EvenQ[n], IntegerDigits[n + 1], IntegerDigits[n + 2]], l}, l = Length[d]; While[l != 1, If[ EvenQ[ d[[l]]], d[[l]]++ ]; If[d[[l]] > 9, d[[l - 1]]++; d[[l]] = 1]; l-- ]; If[ EvenQ[ d[[1]]], d[[1]]++ ]; If[ d[[1]] > 9, d[[1]] = 11]; FromDigits[d]] k = 1; Do[ If[ !PrimeQ[k] && Apply[GCD, Last[ Transpose[ FactorInteger[k]]]] > 1, Print[k]]; k = NextOddNbr[k], {n, 1, 10^8}]

%Y Cf. A001597, A014261, A075787.

%K nonn,base

%O 1,2

%A _Robert G. Wilson v_ and _Zak Seidov_, Oct 11 2002

%E Extended by _Robert G. Wilson v_, Dec 17 2002

%E Terms a(19) and beyond from _Giovanni Resta_, Mar 13 2020