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%I #19 Oct 28 2019 05:08:15
%S 4,1,2,3,26,131,227,301,567,879,3240,11051,8048,38911,7321,97309,
%T 108190,6294,138124,4675268,2687104,1336154,5774420
%N Smallest x > 0 such that gcd(2^x, A004086(2^x)) = 2^n.
%C a(14)=7321, a(17)=6294.
%F a(n) = min{x: gcd(2^x, reverse(2^x))=2^n} = min{x: A055483(x)=2^n}.
%F A072032(a(n)) = 2^n.
%e n=4: a(4)=26 because gcd(2^26, reverse(2^26)) = gcd(67108864, 46880176) = 16 = 2^n.
%t a[n_] := Block[{k=1}, While[ IntegerExponent[ GCD[2^k, FromDigits@ Reverse@ IntegerDigits[2^k]], 2] != n, k++]; k]; Array[a, 13, 0] (* _Giovanni Resta_, Oct 28 2019 *)
%Y Cf. A055483, A004086, A071686, A072032.
%K nonn,base,more
%O 1,1
%A _Labos Elemer_, Jun 07 2002
%E Offset corrected, missing a(3) and a(13)-a(22) added by _Giovanni Resta_, Oct 28 2019