Search: id:A064355
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%I A064355
%S A064355 2,2,2,4,6,10,18,32,56,102,186,340,630,1170,2182,4096,7710,14560,27594,
%T A064355 52428,99858,190650,364722,699040,1342176,2581110,4971008,9586980,
%U A064355 18512790,35791358,69273666,134217728,260300986,505290270,981706806
%N A064355 Number of subsets of {1,2,..n} which sum to 1 mod n.
%H A064355 <a href="Sindx_Su.html#subsetsums">Index entries for sequences related 
               to subset sums modulo m</a>
%F A064355 a(n) = 1/n * sum_{d divides n and d is odd} 2^(n/d) * mu(d); (mu(d) is 
               the Moebius function, sequence A008683).
%e A064355 a(7)=18 because there are 18 subsets of {1,2,3,4,5,6,7} which sum to 
               1 mod 7:{1}, {1,7}, {2,6}, {3,5}, {1,2,5}, {1,3,4}, {2,6,7}, {3,5,
               7}, {4,5,6}, {1,2,5,7}, {1,3,4,7}, {1,3,5,6}, {2,3,4,6}, {4,5,6,7}, 
               {1,2,3,4,5}, {1,3,5,6,7}, {2,3,4,6,7}, {1,2,3,4,5,7}.
%t A064355 f[n_] := Block[{d = Select[Divisors@n, OddQ@ # &]}, Plus @@ (2^(n/d)*MoebiusMu@d)/
               n]; Array[f, 35] (from Robert G. Wilson v (rgwv(at)rgwv.com), Feb 
               20 2006)
%Y A064355 Cf. A063776, A008683. Equals 2*A000048(n).
%Y A064355 Sequence in context: A036654 A010558 A060827 this_sequence A000799 A063823 
               A005865
%Y A064355 Adjacent sequences: A064352 A064353 A064354 this_sequence A064356 A064357 
               A064358
%K A064355 nonn
%O A064355 1,1
%A A064355 Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Sep 25 2001
%E A064355 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 27 2001

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