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A115017 a(n) = largest triangular number dividing n. 2
1, 1, 3, 1, 1, 6, 1, 1, 3, 10, 1, 6, 1, 1, 15, 1, 1, 6, 1, 10, 21, 1, 1, 6, 1, 1, 3, 28, 1, 15, 1, 1, 3, 1, 1, 36, 1, 1, 3, 10, 1, 21, 1, 1, 45, 1, 1, 6, 1, 10, 3, 1, 1, 6, 55, 28, 3, 1, 1, 15, 1, 1, 21, 1, 1, 66, 1, 1, 3, 10, 1, 36, 1, 1, 15, 1, 1, 78, 1, 10, 3, 1, 1, 28, 1, 1, 3, 1, 1, 45, 91, 1, 3, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A083312(n) *(A083312(n) + 1)/2.

EXAMPLE

a(12)=6 because the triangular numbers dividing 12 are 1,3 and 6.

MAPLE

a:=proc(n) local P, j; P:={}: for j from 1 to n do if type(n/(j*(j+1)/2), integer)=true then P:=P union {j*(j+1)/2} else P:=P: fi od: P[nops(P)]; end: seq(a(n), n=1..105); # Emeric Deutsch, Mar 01 2006

MATHEMATICA

With[{trnos=Accumulate[Range[100]]}, Table[Last[Select[trnos, Divisible[ n, #]&]], {n, 100}]] (* Harvey P. Dale, Nov 08 2011 *)

CROSSREFS

Cf. A000217, A083312.

Sequence in context: A324284 A300791 A069972 * A088439 A162315 A109446

Adjacent sequences:  A115014 A115015 A115016 * A115018 A115019 A115020

KEYWORD

nonn

AUTHOR

Leroy Quet, Feb 23 2006

EXTENSIONS

More terms from Emeric Deutsch, Mar 01 2006

STATUS

approved

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Last modified October 18 22:24 EDT 2019. Contains 328211 sequences. (Running on oeis4.)