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%I #7 Aug 15 2015 10:06:57
%S 1,4,80,1285,17831,228289,2782857,32828532,378285281,4282852764,
%T 47828527596,528285275911,5782852759055,62828527590491,
%U 678285275904845,7282852759048382,77828527590483750
%N Number of decimal digits in (10^n)!!.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DoubleFactorial.html">Double Factorial</a>
%Y Cf. A006882.
%K nonn,base
%O 0,2
%A _Eric W. Weisstein_, Nov 30 2005