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%I #17 Feb 14 2024 19:05:55
%S 1,2,9,1953125
%N Exponential primorial: a(n)=prime(n)^a(n-1), a(0)=1, where prime(n)=A000040(n).
%C The next term is too large to include.
%H Jonathan Sondow, <a href="http://mathworld.wolfram.com/ExponentialFactorial.html">Exponential Factorial</a>, Eric Weisstein's World of Mathematics.
%F Sum_{n>=0} 1/a(n) = A167155. - _Amiram Eldar_, Nov 15 2020
%e a(1) = prime(1)^a(0) = 2^1 = 2.
%e a(2) = 3^2 = 9.
%e a(3) = 5^9 = 1953125.
%e a(4) = 7^1953125 has 1650583 digits, starting with 12864794... and ending in ...31920807. - _M. F. Hasler_, Nov 03 2009
%p P:=proc(n) local a,i; a:=2; print(a); for i from 2 by 1 to n do a:=ithprime(i)^a; print(a); od; end: P(5);
%o (PARI) A140319(n)=if(n,prime(n)^A140319(n-1),1) \\ _M. F. Hasler_, Nov 03 2009
%Y Cf. A002110, A049384, A139802, A167155.
%Y Cf. A152859 (alternate definition: start with a(0)=0), A167155.
%K easy,nonn
%O 0,2
%A _Paolo P. Lava_ and _Giorgio Balzarotti_, May 26 2008
%E Corrected offset/definition, and initial a(0)=1 from _M. F. Hasler_, Nov 03 2009
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