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 A177235 The number of non-divisors k of n, 1 < k < n, for which floor(n/k) is odd. 4
 0, 0, 1, 1, 2, 2, 4, 3, 4, 5, 7, 5, 7, 7, 9, 9, 10, 9, 12, 10, 12, 14, 16, 12, 14, 15, 17, 17, 19, 17, 21, 18, 19, 21, 23, 21, 24, 24, 26, 24, 26, 24, 28, 26, 28, 32, 34, 28, 30, 30, 33, 33, 35, 33, 37, 35, 37, 39, 41, 35, 39, 39, 41, 41, 42, 42, 46, 44, 46, 46, 50, 43, 46, 46, 48 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS See the illustration in the second link: a(n) is the number of arcs that are intercepted by a vertical line intersecting the abscissa at n. Sum of the differences of the number of divisors of the largest parts and the number of divisors of the smallest parts of the partitions of n into two parts. - Wesley Ivan Hurt, Jan 05 2017 LINKS Omar E. Pol, Illustration of the number of divisors of n FORMULA a(n) = Sum_{i=1..floor(n/2)} d(n-i) - d(i) where d(n) is the number of divisors of n. - Wesley Ivan Hurt, Jan 05 2017 MAPLE A177235 := proc(n) local a; a :=0 ; for k from 1 to n-1 do if n mod k <> 0 and type(floor(n/k), 'odd') then a := a+1 ; end if; end do: a ; end proc: seq(A177235(n), n=1..120) ; # R. J. Mathar, May 24 2010 CROSSREFS Cf. A000005, A049820. Sequence in context: A015134 A171580 A246796 * A079707 A233511 A205793 Adjacent sequences:  A177232 A177233 A177234 * A177236 A177237 A177238 KEYWORD nonn,easy AUTHOR Omar E. Pol, May 23 2010 EXTENSIONS Terms from a(16) onwards from R. J. Mathar, May 24 2010 STATUS approved

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Last modified January 26 01:48 EST 2020. Contains 331270 sequences. (Running on oeis4.)