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Search: id:A072897
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| A072897 |
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Least n-th order digital invariant which is not an Armstrong number (A005188). |
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+0
1
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OFFSET
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3,1
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COMMENT
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An n-th order digital invariant is a number such that the sum of the n-th power of the integer digits of n equals some number k and the sum of the n-th power of the integer digits of k equals n. An Armstrong number is where n = k.
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REFERENCES
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David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Revised Edition, London, England, 1997, pgs. 124&155.
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LINKS
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Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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MATHEMATICA
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Do[k = 1; While[ !(Apply[Plus, IntegerDigits[Apply[Plus, IntegerDigits[k]^n]]^n] == k && Apply[Plus, IntegerDigits[k]^n] != k), k++ ]; Print[k], {n, 3, 7}]
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CROSSREFS
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Cf. A072409 and A005188.
Sequence in context: A076331 A023070 A015163 this_sequence A071231 A035819 A157880
Adjacent sequences: A072894 A072895 A072896 this_sequence A072898 A072899 A072900
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KEYWORD
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hard,nonn,base
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 09 2002
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