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A175985
a(1) = 1, for n >= 2: a(n) = (a(n-1)+1)^(n-1) - 1.
1
1, 1, 3, 63, 16777215, 1329227995784915872903807060280344575
OFFSET
1,3
COMMENTS
The next term (a(7)) has 217 digits.
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
Sequence in context: A156904 A193100 A053857 * A037108 A249097 A092901
KEYWORD
nonn,easy
AUTHOR
Jaroslav Krizek, Nov 03 2010
STATUS
approved