

A115647


Triangular numbers that are sums of distinct factorials.


2




OFFSET

1,2


COMMENTS

Factorials 0! and 1! are not considered distinct.
A115944(a(n)) > 0; subsequence of A059590.  Reinhard Zumkeller, Feb 02 2006
If there are any terms beyond 40279800 they must be larger than 48!.  Jon E. Schoenfield, Aug 04 2006


LINKS

Table of n, a(n) for n=1..9.


EXAMPLE

1 = T(1) = 1!.
3 = T(2) = 2!+1!.
6 = T(3) = 3!.
120 = T(15) = 5!.
153 = T(17) = 5!+4!+3!+2!+1!.
5886 = T(108) = 7!+6!+5!+3!.
40470 = T(284) = 8!+5!+4!+3!.
41041 = T(286) = 8!+6!+1!.
40279800 = T(8975) = 11!+9!+5!.


MATHEMATICA

triQ[n_] := IntegerQ@Sqrt[8n+1]; fac=Reverse@Range[21]!; lst={}; Do[ n = Plus@@(fac*IntegerDigits[k, 2, 21]); If[triQ[n], AppendTo[lst, n]; Print[{n, k}]], {k, 2^211}]; Union@lst


CROSSREFS

Cf. A025494.
Sequence in context: A046488 A074880 A225884 * A019437 A163423 A083149
Adjacent sequences: A115644 A115645 A115646 * A115648 A115649 A115650


KEYWORD

nonn


AUTHOR

Giovanni Resta, Jan 27 2006


STATUS

approved



