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A140432 a(1)=1, a(2)=2, a(3)=3, a(4)=4, a(5)=5, a(n+1)=a(1)*a(2)*...*a(n)-1 for n>=5.

%I A140432 #5 Jul 08 2022 19:01:47
%S A140432 1,2,3,4,5,119,14279,203904119,41576889949070279,
%T A140432 1728637777837101228675346430208119,
%U A140432 2988188566965591343823377482689473316222062058836342422720083726279
%N A140432 a(1)=1, a(2)=2, a(3)=3, a(4)=4, a(5)=5, a(n+1)=a(1)*a(2)*...*a(n)-1 for n>=5.
%C A140432 a(1)^2 + a(2)^2 + ... + a(70)^2 = a(1)*a(2)*...*a(70)
%H A140432 L. Kurlyandchik <a href="http://kvant.mccme.ru/1995/06/zadachnik_kvanta_matematika.htm">Problem M1523</a>. Kvant 1995 (6), 23; <a href="http://kvant.mccme.ru/1996/03/resheniya_zadachnika_kvanta_ma.htm">Solution to M1523</a>. Kvant 1996 (3), 24-25. (in Russian)
%F A140432 For n>=6, a(n) = a(1)^2 + a(2)^2 + ... + a(n-1)^2 - n + 70.
%t A140432 nxt[{t_,a_}]:={t(t-1),t-1}; Join[{1,2,3,4},NestList[nxt,{120,5},10][[All,2]]] (* _Harvey P. Dale_, Jul 08 2022 *)
%Y A140432 Cf. A005267.
%K A140432 nonn
%O A140432 1,2
%A A140432 _Max Alekseyev_, Jun 19 2008