Search: id:A063776
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%I A063776
%S A063776 2,2,4,4,8,12,20,32,60,104,188,344,632,1172,2192,4096,7712,14572,27596,
%T A063776 52432,99880,190652,364724,699072,1342184,2581112,4971068,9586984,
%U A063776 18512792,35791472,69273668,134217728,260301176,505290272,981706832
%N A063776 Number of subsets of {1,2,..n} which sum to 0 mod n.
%H A063776 T. D. Noe, <a href="b063776.txt">Table of n, a(n) for n=1..200</a>
%H A063776 N. Kitchloo and L. Pachter, <a href="http://math.berkeley.edu/~lpachter/
               papers/modpaper2.pdf">An interesting result about subset sums (pdf)</
               a>
%F A063776 a(n) = 1/n * sum_{d divides n and d is odd} 2^(n/d) * phi(d).
%t A063776 Table[a = Select[ Divisors[n], OddQ[ # ] &]; Apply[Plus, 2^(n/a)*EulerPhi[a]]/
               n, {n, 1, 35}]
%Y A063776 Equals 2*A000016(n). The super-diagonal of A068009. Cf. also A000010, 
               A000013, A051293, A053633. For odd n a(n) = A000031(n) (necklaces).
%Y A063776 Cf. A053636, A054539, A082550.
%Y A063776 Sequence in context: A022476 A000013 A064484 this_sequence A118406 A072488 
               A074818
%Y A063776 Adjacent sequences: A063773 A063774 A063775 this_sequence A063777 A063778 
               A063779
%K A063776 nonn,nice
%O A063776 1,1
%A A063776 Ahmed Fares (ahmedfares(AT)my-deja.com), Aug 16 2001
%E A063776 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Aug 20 2001

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