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 A108220 Numbers n such that concatenating n and the sum of factorials of the digits of n produces a square. 0

%I

%S 3,102,122,202,1102,15031,244134,244233,434412,495918,1267396,1300035,

%T 1324340,1635150,3442657,3878374,5064314,6175125,6181308,10320734,

%U 10560355,10586434,10730603,10804230,11544642,16224135,17523855

%N Numbers n such that concatenating n and the sum of factorials of the digits of n produces a square.

%e 495918 is in the sequence because 4!+9!+5!+9!+1!+8! = 766225 and

%e 495918766225 = 704215^2.

%t sfdsQ[n_]:=Module[{f=Total[IntegerDigits[n]!]},IntegerQ[ Sqrt[ n*10^IntegerLength[ f]+ f]]]; Select[Range[176*10^5],sfdsQ] (* _Harvey P. Dale_, Jul 06 2020 *)

%Y Cf. A061602, A109016.

%K base,nonn

%O 1,1

%A _Jason Earls_, Jun 16 2005

%E Extended by _Don Reble_, Nov 21 2006

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Last modified January 25 17:14 EST 2022. Contains 350572 sequences. (Running on oeis4.)