The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A107757 Numbers k such that Sum_{j=1..k} Catalan(j) == 2 (mod 3). 3
 3, 9, 11, 27, 29, 35, 39, 81, 83, 89, 93, 107, 111, 117, 119, 243, 245, 251, 255, 269, 273, 279, 281, 323, 327, 333, 335, 351, 353, 359, 363, 729, 731, 737, 741, 755, 759, 765, 767, 809, 813, 819, 821, 837, 839, 845, 849, 971, 975, 981, 983, 999, 1001, 1007, 1011 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Y. More, Problem 11165, Amer. Math. Monthly, 112 (2005), 568. MAPLE c:=n->binomial(2*n, n)/(n+1): s:=0: for n from 1 to 1500 do s:=s+c(n): a[n]:=s mod 3: od: A:=[seq(a[n], n=1..1500)]: p:=proc(n) if A[n]=2 then n else fi end: seq(p(n), n=1..1500); # Emeric Deutsch, Jun 12 2005 MATHEMATICA s0 = s2 = {}; s = 0; Do[s = Mod[s + (2 n)!/n!/(n + 1)!, 3]; Switch[ Mod[s, 3], 0, AppendTo[s0, n], 2, AppendTo[s2, n]], {n, 1055}]; s2 (* Robert G. Wilson v, Jun 14 2005 *) CROSSREFS Cf. A000108, A107755, A107756. Equals A074939 - 1. Sequence in context: A032915 A019080 A060141 * A191180 A191128 A057261 Adjacent sequences: A107754 A107755 A107756 * A107758 A107759 A107760 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jun 11 2005 EXTENSIONS More terms from Emeric Deutsch, Jun 12 2005 STATUS approved

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

Last modified December 3 09:50 EST 2022. Contains 358517 sequences. (Running on oeis4.)