This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A303221 Total area of the family of rectangles with dimensions p and p + q such that p and q are both squarefree, n = p + q and p <= q. 0
 0, 2, 3, 12, 10, 24, 21, 48, 45, 80, 66, 168, 143, 154, 120, 272, 306, 288, 247, 640, 525, 594, 437, 936, 800, 1014, 945, 1624, 1160, 1410, 992, 1952, 1551, 2210, 1435, 3348, 2146, 2546, 2106, 3800, 2993, 3360, 3827, 5720, 4905, 4324, 4089, 6816, 5390, 5300 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA a(n) = n * Sum_{i=1..floor(n/2)} i * mu(i)^2 * mu(n-i)^2, where mu is the Möbius function (A008683). MATHEMATICA Table[n*Sum[i*MoebiusMu[i]^2 MoebiusMu[n - i]^2, {i, Floor[n/2]}], {n, 80}] PROG (MAGMA) [0] cat [&+[n*k*MoebiusMu(k)^2*MoebiusMu(n-k)^2: k in [1..Floor(n/2)]]: n in [2..60]]; // Vincenzo Librandi, Apr 21 2018 (PARI) a(n) = n * sum(i=1, n\2, i * moebius(i)^2 * moebius(n-i)^2); \\ Michel Marcus, Apr 21 2018 CROSSREFS Cf. A008683, A261985. Sequence in context: A075711 A079077 A027611 * A168059 A068550 A093432 Adjacent sequences:  A303218 A303219 A303220 * A303222 A303223 A303224 KEYWORD nonn,easy AUTHOR Wesley Ivan Hurt, Apr 19 2018 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 15 11:43 EST 2019. Contains 329999 sequences. (Running on oeis4.)