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A070308 "Canada perfect numbers": n such that the sum of digits^2 of n equals the sum of d|n, 1<d<n. 4
125, 581, 8549, 16999 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

There is no such number > 10^6. Those numbers were defined by mathematicians from Manitoba University for the 125th anniversary of Canada.

REFERENCES

J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 125, p. 43, Ellipses, Paris 2008.

Jean-Marie De Koninck and Armel Mercier, Introduction a la theorie des nombres, Collection Universitaire de Mathematiques, Modulo, p. 85.

J.-M. De Koninck and A. Mercier, 1001 Problemes en Theorie Classique Des Nombres, Problem 700 pp. 91; 299, Ellipses Paris 2004.

LINKS

Table of n, a(n) for n=1..4.

MATHEMATICA

cnQ[n_]:=Module[{sod=Total[Rest[Most[Divisors[n]]]]}, sod == Total[IntegerDigits[n]^2]];  Select[Range[2, 17000], cnQ]  (* Harvey P. Dale, Jun 17 2011 *)

CROSSREFS

Sequence in context: A061450 A067974 A034290 * A211176 A045170 A235896

Adjacent sequences:  A070305 A070306 A070307 * A070309 A070310 A070311

KEYWORD

nonn,base,easy,fini,full

AUTHOR

Benoit Cloitre, May 12 2002

EXTENSIONS

There are no further terms. - David Wasserman, May 13 2003

STATUS

approved

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Last modified December 20 18:44 EST 2014. Contains 252288 sequences.