This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A060423 Number of obtuse triangles made from vertices of a regular n-gon. 2
 0, 0, 0, 0, 0, 5, 6, 21, 24, 54, 60, 110, 120, 195, 210, 315, 336, 476, 504, 684, 720, 945, 990, 1265, 1320, 1650, 1716, 2106, 2184, 2639, 2730, 3255, 3360, 3960, 4080, 4760, 4896, 5661, 5814, 6669, 6840, 7790, 7980, 9030, 9240, 10395, 10626 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 LINKS FORMULA a(n) = n*(n-1)*(n-3)/8 when n odd; n*(n-2)*(n-4)/8 when n even. G.f.: x^5*(x+5)/((1-x)(1-x^2)^3). - Michael Somos, Jan 30 2004 For n odd, a(n) = A080838(n). - Gerald McGarvey, Sep 14 2008 a(n) = n*(2*n-3-(-1)^n)*(2*n-7-(-1)^n)/32. - Wesley Ivan Hurt, Dec 31 2013 MAPLE A060423:=n->n*(2*n-3-(-1)^n)*(2*n-7-(-1)^n)/32; seq(A060423(n), n=0..100); # Wesley Ivan Hurt, Dec 31 2013 MATHEMATICA Table[n(2n-3-(-1)^n)(2n-7-(-1)^n)/32, {n, 0, 100}] (* Wesley Ivan Hurt, Dec 31 2013 *) Table[If[EvenQ[n], (n(n-2)(n-4))/8, (n(n-1)(n-3))/8], {n, 0, 50}] (* Harvey P. Dale, Sep 18 2018 *) PROG (PARI) a(n)=polcoeff(x^5*(5+x)/(1-x)/(1-x^2)^3+x*O(x^n), n) (MAGMA) [n*(2*n-3-(-1)^n)*(2*n-7-(-1)^n)/32 : n in [0..60]]; // Wesley Ivan Hurt, Apr 14 2017 CROSSREFS Cf. A000330, A007290, A046092. Sequence in context: A231181 A259775 A057520 * A037951 A095308 A132796 Adjacent sequences:  A060420 A060421 A060422 * A060424 A060425 A060426 KEYWORD easy,nice,nonn AUTHOR Sen-Peng Eu, Apr 05 2001 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 July 21 19:51 EDT 2019. Contains 325199 sequences. (Running on oeis4.)
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "url": "http://oeis.org/A060423", "fetch_time": 1563753141000000000, "content_mime_type": "text/html", "warc_filename": "crawl-data/CC-MAIN-2019-30/segments/1563195527396.78/warc/CC-MAIN-20190721225759-20190722011759-00020.warc.gz", "warc_record_offset": 115287156, "warc_record_length": 4183, "token_count": 785, "char_count": 1855, "score": 3.625, "int_score": 4, "crawl": "CC-MAIN-2019-30", "snapshot_type": "latest", "language": "en", "language_score": 0.44053220748901367, "file_path": "/sailhome/yjruan/project/latent-lm/data/processed/finemath-4plus/finemath-4plus/train-00000-of-00064.parquet"}