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A129619 a(n) = largest proper divisor of the sum of all positive integers which are <= n and are not included among the first n-1 terms of the sequence. 0
1, 1, 1, 3, 1, 1, 12, 16, 1, 17, 31, 31, 25, 1, 52, 52, 52, 61, 47, 23, 91, 102, 102, 114, 114, 127, 1, 103, 169, 184, 184, 200, 1, 1, 251, 269, 115, 1, 326, 346, 1, 155, 409, 431, 1, 1, 1, 143, 525, 550, 1, 1, 602, 629, 101, 37, 463, 1, 753, 783, 783, 814, 89, 585, 910, 943 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..66.

EXAMPLE

The positive integers which are <= 8 and do not occur among the first 7 terms of the sequence are 2,4,5,6,7,8. a(8) is the largest proper divisor of the sum of these integers. 2+4+5+6+7+8 = 32. So a(8) is the largest proper divisor of 32, which is 16.

MATHEMATICA

a = {1}; For[n = 2, n < 70, n++, AppendTo[a, Divisors[n*(n + 1)/2 - Plus @@ Select[Union[a, a], # < n + 1 &]][[ -2]]]]; a (* Stefan Steinerberger, Nov 21 2007 *)

CROSSREFS

Sequence in context: A128592 A156584 A209424 * A094573 A055154 A338875

Adjacent sequences:  A129616 A129617 A129618 * A129620 A129621 A129622

KEYWORD

nonn

AUTHOR

Leroy Quet, May 30 2007

EXTENSIONS

More terms from Stefan Steinerberger, Nov 21 2007

STATUS

approved

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Last modified June 18 15:01 EDT 2021. Contains 345120 sequences. (Running on oeis4.)