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A056454
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Palindromes using exactly three different symbols.
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3
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0, 0, 0, 0, 6, 6, 36, 36, 150, 150, 540, 540, 1806, 1806, 5796, 5796, 18150, 18150, 55980, 55980, 171006, 171006, 519156, 519156, 1569750, 1569750, 4733820, 4733820, 14250606, 14250606, 42850116, 42850116, 128746950, 128746950
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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REFERENCES
| M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia.
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FORMULA
| 3! * stirling2( [(n+1)/2], 3).
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MAPLE
| with(combinat, stirling2):A056454:=n->3!*stirling2(floor((n+1)/2), 3); (C. Ronaldo)
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CROSSREFS
| Cf. A056449, A001117.
Sequence in context: A165827 A111437 A056464 * A056452 A183622 A176861
Adjacent sequences: A056451 A056452 A056453 * A056455 A056456 A056457
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KEYWORD
| nonn,base
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AUTHOR
| Marks R. Nester (nesterm(AT)dpi.qld.gov.au)
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