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A108241 Numbers n such that concatenating n and the sum of factorials of the digits of n produces a triangular number. 0
0, 3, 18, 122, 2111, 12442, 40850, 113347, 202343, 233506, 332600, 435405, 525544, 546233, 554161, 716795, 1000334, 1016217, 1142240, 1244630, 2240515, 2414603, 3103412, 3203757, 3400440, 3413651, 3424213, 3461244, 4430222, 5226150 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..30.

EXAMPLE

18 is in the sequence because 1!+8! = 40321 and 1918*1919/2 = 1840321.

MATHEMATICA

ctnQ[n_]:=Module[{idn=IntegerDigits[n], c}, c=FromDigits[Join[idn, IntegerDigits[ Total[idn!]]]]; IntegerQ[(Sqrt[8c+1]-1)/2]]; Select[ Range[0, 5300000], ctnQ] (* Harvey P. Dale, Sep 20 2012 *)

CROSSREFS

Cf. A061602, A109016.

Sequence in context: A127188 A074558 A074564 * A199421 A305869 A181998

Adjacent sequences:  A108238 A108239 A108240 * A108242 A108243 A108244

KEYWORD

base,nonn

AUTHOR

Jason Earls, Jun 17 2005

STATUS

approved

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Last modified May 28 17:37 EDT 2020. Contains 334684 sequences. (Running on oeis4.)