This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A008217 Floor(n/4)*floor((n+1)/4). 3
 0, 0, 0, 0, 1, 1, 1, 2, 4, 4, 4, 6, 9, 9, 9, 12, 16, 16, 16, 20, 25, 25, 25, 30, 36, 36, 36, 42, 49, 49, 49, 56, 64, 64, 64, 72, 81, 81, 81, 90, 100, 100, 100, 110, 121, 121, 121, 132, 144, 144, 144, 156, 169, 169, 169, 182, 196, 196, 196, 210, 225, 225, 225, 240, 256, 256, 256, 272, 289, 289, 289, 306 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,8 COMMENTS Oblong numbers, squares and quarter-squares are subsequences: a(A004767(n))=A002378(N); a(A008586(n))=A000290(n); a(A005408(n))=A002620(n). [Reinhard Zumkeller, Oct 09 2011] LINKS Reinhard Zumkeller, Table of n, a(n) for n = 0..10000 FORMULA Empirical g.f.: -x^4*(x^2-x+1) / ((x-1)^3*(x+1)*(x^2+1)^2). - Colin Barker, Mar 31 2013 PROG (Haskell) a008217 n = a008217_list !! n a008217_list = zipWith (*) (tail qs) qs where qs = map (`div` 4) [0..] -- Reinhard Zumkeller, Oct 09 2011 (PARI) a(n) = floor(n/4)*floor((n+1)/4); /* Joerg Arndt, Mar 31 2013 */ CROSSREFS Sequence in context: A023819 A201629 A033827 * A170889 A182839 A043552 Adjacent sequences:  A008214 A008215 A008216 * A008218 A008219 A008220 KEYWORD nonn AUTHOR EXTENSIONS Cf. A008133. 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 23 20:19 EDT 2018. Contains 316530 sequences. (Running on oeis4.)