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A063776
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Number of subsets of {1,2,..n} which sum to 0 mod n.
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9
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2, 2, 4, 4, 8, 12, 20, 32, 60, 104, 188, 344, 632, 1172, 2192, 4096, 7712, 14572, 27596, 52432, 99880, 190652, 364724, 699072, 1342184, 2581112, 4971068, 9586984, 18512792, 35791472, 69273668, 134217728, 260301176, 505290272, 981706832
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..200
N. Kitchloo and L. Pachter, An interesting result about subset sums (pdf)
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FORMULA
| a(n) = 1/n * sum_{d divides n and d is odd} 2^(n/d) * phi(d).
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MATHEMATICA
| Table[a = Select[ Divisors[n], OddQ[ # ] &]; Apply[Plus, 2^(n/a)*EulerPhi[a]]/n, {n, 1, 35}]
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CROSSREFS
| Equals 2*A000016(n). The super-diagonal of A068009. Cf. also A000010, A000013, A051293, A053633. For odd n a(n) = A000031(n) (necklaces).
Cf. A053636, A054539, A082550.
Sequence in context: A022476 A000013 A064484 * A118406 A072488 A074818
Adjacent sequences: A063773 A063774 A063775 * A063777 A063778 A063779
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KEYWORD
| nonn,nice
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AUTHOR
| Ahmed Fares (ahmedfares(AT)my-deja.com), Aug 16 2001
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Aug 20 2001
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