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 A072897 Least n-th order digital invariant which is not an Armstrong number (A005188), or 0 if no such term exists. 1
 136, 2178, 58618, 63804, 2755907, 0, 144839908, 304162700, 4370652168, 0, 0, 0, 0, 0, 21914086555935085, 187864919457180831, 0, 13397885590701080090, 0, 0, 0, 19095442247273220984552, 1553298727699254868304830, 1539325689516673750004702, 242402817739393059296681797 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 COMMENTS An n-th order digital invariant is a number such that the sum of the n-th powers of the integer digits of n equals some number k and the sum of the n-th powers of the integer digits of k equals n. An Armstrong number is where n = k. REFERENCES David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Revised Edition, London, England, 1997, pgs. 124&155. LINKS Tim Johannes Ohrtmann, Table of n, a(n) for n = 3..45 Eric Weisstein's World of Mathematics, Invariant. MATHEMATICA 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}] CROSSREFS Cf. A072409 and A005188. Sequence in context: A015163 A235190 A249985 * A254703 A250424 A251940 Adjacent sequences:  A072894 A072895 A072896 * A072898 A072899 A072900 KEYWORD hard,nonn,base AUTHOR Robert G. Wilson v, Aug 09 2002 EXTENSIONS a(8)-a(27) from Tim Johannes Ohrtmann, Aug 27 2015 STATUS approved

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