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A115017
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a(n) = largest triangular number dividing n.
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2
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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; internal format)
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OFFSET
| 1,3
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 1..1000
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FORMULA
| a(n) = A083312(n) *(A083312(n) +1)/2.
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EXAMPLE
| a(12)=6 because the triangular numbers dividing 12 are 1,3 and 6.
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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 (deutsch(AT)duke.poly.edu), Mar 01 2006
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MATHEMATICA
| With[{trnos=Accumulate[Range[100]]}, Table[Last[Select[trnos, Divisible[ n, #]&]], {n, 100}]] (* From Harvey P. Dale, Nov 08 2011 *)
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CROSSREFS
| Cf. A000217, A083312.
Sequence in context: A195892 A195522 A069972 * A088439 A162315 A109446
Adjacent sequences: A115014 A115015 A115016 * A115018 A115019 A115020
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Feb 23 2006
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 01 2006
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