A072897 Least n-th order digital invariant which is not an Armstrong number (A005188), or 0 if no such term exists.

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

Offset

3,1

Comments

An n-th order digital invariant is a number such that the sum of the n-th powers of the digits of n equals some number k and the sum of the n-th powers of the 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, pp. 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. A005188, A072409.

Sequence in context: A015163 A235190 A249985 * A254703 A333110 A250424

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