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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 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: A072329 A068630 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 January 21 11:21 EST 2019. Contains 319354 sequences. (Running on oeis4.)