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Base 6 also has four factorions, as does base 15. - Alonso del Arte, Oct 20 2012
J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 145, p. 50, Ellipses, Paris 2008.
Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see pp. 68, 305.
Joe Roberts, "The Lure of the Integers", page 35.
D. Wells, Curious and interesting numbers, Penguin Books, p. 125.
Table of n, a(n) for n=1..4.
Project Euler, Problem 34
Eric Weisstein's World of Mathematics, Factorion
1! + 4! + 5! = 1 + 24 + 120 = 145, therefore 145 is in the sequence.
Select[Range, Plus @@ (IntegerDigits[ # ]!) == # &] (* Alonso del Arte, Jan 14 2008 *)
Sequence in context: A188284 A228507 A071064 * A182478 A214910 A110624
Adjacent sequences: A014077 A014078 A014079 * A014081 A014082 A014083
David W. Wilson
Additional reference from Felice Russo.