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Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GeneralizedFermatNumber.html">Generalized Fermat Number</a>.
OEIS Wiki, <a href="/wiki/Generalized_Fermat_numbers">Generalized Fermat numbers</a>.
a(0) = 12, a(1) = 122; a(n) = a(n-1) + 10*11^(2^(n-1))*product_Product_{i=0..n-2} a(i), n >= 2.
a(0) = 12; a(n) = 10*(product_Product_{i=0..n-1} a(i)) + 2, n >= 1.
Sum_{n>=0} 2^n/a(n) = 1/10. - Amiram Eldar, Oct 03 2022
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(MAGMAMagma) [11^2^n+1 : n in [0..6]]
_Arkadiusz Wesolowski (wesolowski(AT)aol.pl), _, Nov 08 2011
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a(0) = 12; a(n) = 2 + 10*(product_{i=0..n-1} a(i), ) + 2, n >= 1.