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A242287 Greedy-summable triangular numbers. 4
10, 21, 28, 45, 55, 66, 91, 105, 120, 136, 171, 190, 231, 253, 300, 325, 378, 406, 435, 496, 528, 595, 630, 666, 703, 780, 820, 903, 946, 1035, 1081, 1176, 1225, 1326, 1378, 1485, 1540, 1596, 1711, 1770, 1891, 1953, 2080, 2145, 2211, 2278, 2415, 2485, 2628 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Greedy summability is defined at A242284.

LINKS

Clark Kimberling, Table of n, a(n) for n = 1..1000

EXAMPLE

Let s(n) = n(n+1)/2 = A000217(n).  Then

a(1) = 10 = 6 + 3 + 1;

a(2) = 21 = 15 + 6;

a(3) = 28 = 21 + 6 + 1;

a(4) = 45 = 36 + 6 + 3.

MATHEMATICA

z = 200;  s = Table[n (n + 1)/2, {n, 1, z}]; t = Table[{s[[n]], #, Total[#] == s[[n]]} &[DeleteCases[-Differences[FoldList[If[#1 - #2 >= 0, #1 - #2, #1] &, s[[n]], Reverse[Select[s, # < s[[n]] &]]]], 0]], {n, z}]

r[n_] := s[[n]] - Total[t[[n]][[2]]];

tr = Table[r[n], {n, 2, z}]  (* A242284 *)

c = Table[Length[t[[n]][[2]]], {n, 2, z}] (* A242285 *)

f = 1 + Flatten[Position[tr, 0]]  (* A242286 *)

f (f + 1)/2  (* A242287 *) (* Peter J. C. Moses, May 06 2014 *)

CROSSREFS

Cf. A242284, A242285, A242286, A241833, A000217.

Sequence in context: A181450 A087597 A087598 * A165403 A097386 A108685

Adjacent sequences:  A242284 A242285 A242286 * A242288 A242289 A242290

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, May 10 2014

STATUS

approved

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Last modified June 26 20:37 EDT 2019. Contains 324380 sequences. (Running on oeis4.)