|
Search: id:A072884
|
|
|
| A072884 |
|
3rd order digital invariants: the sum of the cubes of the digits of n equals some number k and the sum of the cubes of the digits of k equals n. |
|
+0
3
|
| |
|
|
OFFSET
|
1,2
|
|
|
REFERENCES
|
David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Revised Edition, London, England, 1997, pgs. 124&125.
J.-M. De Koninck and A. Mercier, 1001 Problemes en Theorie Classique Des Nombres, Problem 257 pp. 41;185 Ellipses Paris 2004.
|
|
FORMULA
|
n such that f(f(n))=n, where f(k)=A055012(k). - Lekraj Beedassy (blekraj(AT)yahoo.com), Sep 10 2004
|
|
EXAMPLE
|
136 is included because 1^3 + 3^3 + 6^3 = 244 and 2^3 + 4^3 + 4^3 = 136.
244 is included because 2^3 + 4^3 + 4^3 = 136 and 1^3 + 3^6 + 6^3 = 244.
|
|
MATHEMATICA
|
f[n_] := Apply[Plus, IntegerDigits[Apply[Plus, IntegerDigits[n]^3]]^3]; Select[ Range[10^7], f[ # ] == # &]
Select[Range[10000], Plus@@IntegerDigits[Plus@@IntegerDigits[ # ]^3]^3)== #&]
|
|
CROSSREFS
|
Cf. A072409.
Sequence in context: A051307 A056740 A065663 this_sequence A072889 A101335 A098215
Adjacent sequences: A072881 A072882 A072883 this_sequence A072885 A072886 A072887
|
|
KEYWORD
|
nonn,fini,full,base
|
|
AUTHOR
|
Robert G. Wilson v (rgwv(AT)rgwv.com) and Harvey P. Dale (hpd1(AT)nyu.edu), Aug 09 2002
|
|
|
Search completed in 0.002 seconds
|
