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 A140319 Exponential primorial: a(n)=prime(n)^a(n-1), a(0)=1, where prime(n)=A000040(n). 2

%I

%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 J. Sondow, <a href="http://mathworld.wolfram.com/ExponentialFactorial.html">"Exponential Factorial."</a>

%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.

%Y Cf. A152859 (alternate definition: start with a(0)=0), A167155. [M. F. Hasler, Nov 03 2009]

%K easy,nonn

%O 0,2

%A _Paolo P. Lava_ and _Giorgio Balzarotti_, May 26 2008

%E Corrected offset/definition, added initial term a(0)=1 _M. F. Hasler_, Nov 03 2009

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