A175985 - OEIS

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A175985

a(1) = 1, for n >= 2: a(n) = (a(n-1)+1)^(n-1) - 1.

%I #13 Apr 25 2016 11:45:31

%S 1,1,3,63,16777215,1329227995784915872903807060280344575

%N a(1) = 1, for n >= 2: a(n) = (a(n-1)+1)^(n-1) - 1.

%C The next term (a(7)) has 217 digits.

%F a(n+1) = 2^A000142(n) - 1; A000142 = factorial numbers.

%e For n = 4: a(4) = (3+1)^3 - 1 = 63.

%o (PARI) a(n)=if(n<=1,1,(a(n-1)+1)^(n-1)-1); /* _Joerg Arndt_, Jun 10 2011 */

%K nonn,easy

%O 1,3

%A _Jaroslav Krizek_, Nov 03 2010