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A199493
2*8^n+1.
3
3, 17, 129, 1025, 8193, 65537, 524289, 4194305, 33554433, 268435457, 2147483649, 17179869185, 137438953473, 1099511627777, 8796093022209, 70368744177665, 562949953421313, 4503599627370497, 36028797018963969
OFFSET
0,1
COMMENTS
An Engel expansion of 4 to the base 8 as defined in A181565, with the associated series expansion 4 = 8/3 + 8^2/(3*17) + 8^3/(3*17*129) + 8^4/(3*17*129*1025) + .... Cf. A087289 and A199552. - Peter Bala, Oct 30 2013
FORMULA
a(n) = 8*a(n-1)-7.
a(n) = 9*a(n-1)-8*a(n-2).
G.f.: (3-10*x)/((1-x)*(1-8*x)).
PROG
(Magma) [2*8^n+1: n in [0..30]];
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 07 2011
STATUS
approved