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A111638 Numbers having a unique partition into three positive triangular numbers. 6
3, 5, 7, 8, 9, 10, 13, 14, 15, 16, 18, 24, 25, 36, 38, 50, 53, 55, 60, 69, 81, 83, 99, 110, 119 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A063993(a(n)) = 1. - Reinhard Zumkeller, Jul 20 2012

LINKS

Table of n, a(n) for n=1..25.

EXAMPLE

Example: 119=55+36+28

MATHEMATICA

trig[n_]:=n(n+1)/2; trigInv[x_]:=Ceiling[Sqrt[Max[0, 2x]]]; lim=100; nLst=Table[0, {trig[lim]}]; Do[n=trig[a]+trig[b]+trig[c]; If[n>0 && n<=trig[lim], nLst[[n]]++ ], {a, 1, lim}, {b, a, trigInv[trig[lim]-trig[a]]}, {c, b, trigInv[trig[lim]-trig[a]-trig[b]]}]; Flatten[Position[nLst, 1]]

CROSSREFS

Cf. A060773 (n having a unique partition into three nonnegative triangular numbers).

Cf. A002097, A064825.

Sequence in context: A173186 A335575 A047746 * A324334 A080262 A025050

Adjacent sequences:  A111635 A111636 A111637 * A111639 A111640 A111641

KEYWORD

fini,full,nonn

AUTHOR

T. D. Noe, Aug 10 2005

STATUS

approved

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Last modified April 18 16:51 EDT 2021. Contains 343089 sequences. (Running on oeis4.)