This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A076664 a(n) = Sum_{k=1..n} antisigma(k), where antisigma(i) = sum of the nondivisors of i that are between 1 and i. 5
 0, 0, 2, 5, 14, 23, 43, 64, 96, 133, 187, 237, 314, 395, 491, 596, 731, 863, 1033, 1201, 1400, 1617, 1869, 2109, 2403, 2712, 3050, 3400, 3805, 4198, 4662, 5127, 5640, 6181, 6763, 7338, 8003, 8684, 9408, 10138, 10957, 11764, 12666, 13572, 14529, 15538 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Sum of all proper nondivisors of all positive integers <= n. - Omar E. Pol, Feb 11 2014 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 FORMULA a(n) = A000292(n) - A024916(n), n >= 1. Omar E. Pol, Feb 11 2014 a(n) = Sum_{k=1..n} Sum_{i=1..k-1} (n-k-i+1) mod (n-i+1). - Wesley Ivan Hurt, Sep 13 2017 G.f.: x/(1 - x)^4 - (1/(1 - x))*Sum_{k>=1} k*x^k/(1 - x^k). - Ilya Gutkovskiy, Sep 18 2017 EXAMPLE a(5) = antisigma(1) + ... + antisigma(5) = 0 + 0 + 2 + 3 + 9 = 14. MATHEMATICA l = {}; s = 0; Do[s = s + (n (n + 1) / 2) - DivisorSigma[1, n]; l = Append[l, s], {n, 1, 100}]; l Accumulate[Table[Total[Complement[Range[n], Divisors[n]]], {n, 50}]] (* Harvey P. Dale, May 19 2014 *) PROG (PARI) a(n) = sum(k=1, n, k*(k+1)/2-sigma(k)); \\ Michel Marcus, Sep 18 2017 CROSSREFS Cf. A024816, A000292, A024916. Sequence in context: A176191 A265248 A131661 * A220477 A049939 A296302 Adjacent sequences:  A076661 A076662 A076663 * A076665 A076666 A076667 KEYWORD nonn,easy AUTHOR Joseph L. Pe, Oct 24 2002 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 19 05:24 EDT 2018. Contains 316336 sequences. (Running on oeis4.)