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A068627 a(0) = 0, a(n) = a(n-1) + n if n does not divide a(n-1). a(n) = a(n-1) - n if n divides a(n-1). a(n) = n if a(n-1) = 0. 3
0, 1, 3, 0, 4, 9, 15, 22, 30, 39, 49, 60, 48, 61, 75, 60, 76, 93, 111, 130, 150, 171, 193, 216, 192, 217, 243, 216, 244, 273, 303, 334, 366, 399, 433, 468, 432, 469, 507, 468, 508, 549, 591, 634, 678, 723, 769, 816, 768, 817, 867, 816, 868, 921, 975, 1030, 1086 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

The sequence is not monotonically increasing but has an increasing trend with some nodes i.e. numbers occurring twice in the sequence like 60 etc. Are there infinitely many nodes in the sequence.?

LINKS

Table of n, a(n) for n=0..56.

EXAMPLE

Since 12 divides a(11)=60, a(12) = 60 - 12 = 48.

Since 13 does not divide a(12)=48, a(13) = 48 + 13 = 61.

PROG

(PARI) lista(nn) = {preca = 0; for (n=1, nn, print1(preca, ", "); if (preca == 0, nexta = n, if (preca % n, nexta = preca + n, nexta = preca - n); ); preca = nexta; ); } \\ Michel Marcus, Jan 23 2014

CROSSREFS

Cf. A068626.

Sequence in context: A068630 A309764 A079406 * A074171 A180657 A094665

Adjacent sequences:  A068624 A068625 A068626 * A068628 A068629 A068630

KEYWORD

easy,nonn

AUTHOR

Amarnath Murthy, Feb 26 2002

STATUS

approved

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Last modified March 30 06:59 EDT 2020. Contains 333119 sequences. (Running on oeis4.)