A175985 - OEIS

A175985

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

1, 1, 3, 63, 16777215, 1329227995784915872903807060280344575

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OFFSET

1,3

COMMENTS

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

LINKS

FORMULA

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

EXAMPLE

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

PROG

(PARI) a(n)=if(n<=1, 1, (a(n-1)+1)^(n-1)-1); /* Joerg Arndt, Jun 10 2011 */

CROSSREFS

KEYWORD

nonn,easy

AUTHOR

STATUS

approved