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 A175150 a(1)=0. If d(n)>d(n-1), then a(n)=a(n-1)+1. If d(n)
 0, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 3, 2, 3, 2, 3, 2, 2, 1, 2, 1, 2, 2, 3, 2, 3, 2, 3, 2, 2, 2, 3, 2, 3, 3, 4, 3, 4, 3, 4, 4, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 2, 1, 2, 1, 2, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 3, 4, 5, 5, 4, 5, 4, 5, 4, 3, 2, 3, 2, 2, 2, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS For n >=2, a(n) = (the number of k <= n where d(k) > d(k-1)) - (the number of k <= n where d(k) < d(k-1)). The record values of {a(n)} occur at n= 1, 2, 4, 16, 40, 75, 165, 208,... This sequence goes negative at n = 647. In the plot of the first 10^6 terms, the graph is mostly negative after about 250000. - T. D. Noe, Apr 27 2012 LINKS T. D. Noe, Table of n, a(n) for n = 1..10000 T. D. Noe, Plot of 10^6 terms MATHEMATICA Join[{0}, Accumulate[Sign[Differences[DivisorSigma[0, Range[100]]]]]] (* T. D. Noe, Apr 27 2012 *) CROSSREFS Cf. A000005, A182394 (first differences). Sequence in context: A161278 A160982 A334541 * A161236 A161060 A161264 Adjacent sequences:  A175147 A175148 A175149 * A175151 A175152 A175153 KEYWORD sign AUTHOR Leroy Quet, Feb 24 2010 EXTENSIONS Extended by Ray Chandler, Mar 03 2010 Comment typo corrected by Leroy Quet, Mar 07 2010 STATUS approved

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Last modified November 26 21:07 EST 2021. Contains 349344 sequences. (Running on oeis4.)