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A231712
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a(n) = n^n + n - 1.
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5
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0, 1, 5, 29, 259, 3129, 46661, 823549, 16777223, 387420497, 10000000009, 285311670621, 8916100448267, 302875106592265, 11112006825558029, 437893890380859389, 18446744073709551631, 827240261886336764193, 39346408075296537575441, 1978419655660313589123997
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OFFSET
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0,3
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COMMENTS
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Supersequence of A187605 (primes of the form n^n + n - 1).
Numbers n such that a(n) = prime: 2, 3, 19, 30, 535, 1551, ..., another term > 2300 (see A058912 and A187605).
Also generalization of the problem: "What is the minimum length of a text consisting only of the first n letters of the alphabet and containing all possible n-tuples (no blanks)?" (see Puzzleup link). Example for n = 3, length of text a(3) = 29: AAABAACABBABCACBACCBBBCBCCCAA, all triples (AAA, AAB, ..., CCC) occurring exactly once. - Jörg Zurkirchen, Sep 06 2014
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LINKS
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FORMULA
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E.g.f.: 1/(1 + LambertW(-x)) + (x-1)*exp(x). - Alois P. Heinz, Jun 15 2018
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MAPLE
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MATHEMATICA
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Join[{0}, Table[n^n + n - 1, {n, 18}]]
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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