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!)
 A213907 a(n) = 1 + n + n*{n/2} + n*{n/2}*{n/3} + n*{n/2}*{n/3}*{n/4} +... where {x} = [x+1/2] = round(x). 0
 1, 3, 9, 34, 61, 261, 709, 1324, 4937, 15040, 28561, 107262, 248341, 522445, 1972363, 7591936, 8835345, 26421129, 145475533, 183752250, 701184621, 2234736295, 2996725227, 15105451596, 32483720761, 77618520551, 217809217211, 625456400842, 1638545943301 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS EXAMPLE a(2) = 1 + 2 + 2*1 + 2*1*1 + 2*1*1*1 = 9 a(3) = 1 + 3 + 3*2 + 3*2*1 + 3*2*1*1 + 3*2*1*1*1 + 3*2*1*1*1*1 = 34. PROG (PARI) {a(n)=1+sum(m=1, 2*n, prod(k=1, m, round(n/k)))} for(n=0, 60, print1(a(n), ", ")) CROSSREFS Cf. A075885. Sequence in context: A097677 A138769 A100076 * A148999 A149000 A160963 Adjacent sequences:  A213904 A213905 A213906 * A213908 A213909 A213910 KEYWORD nonn AUTHOR Paul D. Hanna, Jun 24 2012 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 6 14:47 EST 2019. Contains 329806 sequences. (Running on oeis4.)