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Search: id:A000208
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| A000208 |
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Number of even sequences with period 2n.
(Formerly M2377 N0943)
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+0
2
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| 1, 1, 3, 4, 12, 28, 94, 298, 1044, 3658, 13164, 47710, 174948, 645436, 2397342, 8948416, 33556500, 126324496, 477225962, 1808414182, 6871973952, 26178873448, 99955697946, 382438918234, 1466015854100, 5629499869780
(list; graph; listen)
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OFFSET
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0,3
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REFERENCES
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E. N. Gilbert and J. Riordan, Symmetry types of periodic sequences, Illinois J. Math., 5 (1961), 657-665.
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FORMULA
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a(n) = (A000013(2*n)+A000013(n))/2 if n odd or A000013(2*n)/2 if n even.
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PROGRAM
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(PARI) {A000208(n)=if(n%2==0, (A000013(2*n)+A000013(n))/2, A000013(2*n)/2)}
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CROSSREFS
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Cf. A000013, A000206.
Adjacent sequences: A000205 A000206 A000207 this_sequence A000209 A000210 A000211
Sequence in context: A000207 A002986 A090660 this_sequence A079154 A101716 A109771
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KEYWORD
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nonn,easy,nice
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AUTHOR
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njas
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EXTENSIONS
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More terms and formula from Randall L. Rathbun, Jan 11 2002
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