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A072033
Smallest x > 0 such that gcd(2^x, A004086(2^x)) = 2^n.
0
4, 1, 2, 3, 26, 131, 227, 301, 567, 879, 3240, 11051, 8048, 38911, 7321, 97309, 108190, 6294, 138124, 4675268, 2687104, 1336154, 5774420
OFFSET
1,1
COMMENTS
a(14)=7321, a(17)=6294.
FORMULA
a(n) = min{x: gcd(2^x, reverse(2^x))=2^n} = min{x: A055483(x)=2^n}.
A072032(a(n)) = 2^n.
EXAMPLE
n=4: a(4)=26 because gcd(2^26, reverse(2^26)) = gcd(67108864, 46880176) = 16 = 2^n.
MATHEMATICA
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 *)
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Labos Elemer, Jun 07 2002
EXTENSIONS
Offset corrected, missing a(3) and a(13)-a(22) added by Giovanni Resta, Oct 28 2019
STATUS
approved