%I #28 Jan 06 2023 21:22:20
%S 1,3,9,220
%N a(n) is the smallest m such that A090822(m) = n.
%H D. C. Gijswijt, <a href="https://pyth.eu/uploads/user/ArchiefPDF/Pyth55-3.pdf">Krulgetallen</a>, Pythagoras, 55ste Jaargang, Nummer 3, Jan 2016. (Shows that the sequence is infinite)
%H F. J. van de Bult, D. C. Gijswijt, J. P. Linderman, N. J. A. Sloane and Allan Wilks, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL10/Sloane/sloane55.html">A Slow-Growing Sequence Defined by an Unusual Recurrence</a>, J. Integer Sequences, Vol. 10 (2007), #07.1.2.
%H F. J. van de Bult, D. C. Gijswijt, J. P. Linderman, N. J. A. Sloane and Allan Wilks, A Slow-Growing Sequence Defined by an Unusual Recurrence [<a href="http://neilsloane.com/doc/gijs.pdf">pdf</a>, <a href="http://neilsloane.com/doc/gijs.ps">ps</a>].
%H <a href="/index/Ge#Gijswijt">Index entries for sequences related to Gijswijt's sequence</a>
%F a(n) is about 2^(2^(3^(4^(5^...^(n-1))))).
%Y Cf. A090822.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, based on a suggestion from Dion Gijswijt (gijswijt(AT)science.uva.nl), Mar 04 2004
%E Sequence is infinite but next term, about 10^(10^23.09987) (see A091787), is too large to include.