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 A004201 Accept one, reject one, accept two, reject two, ... 12
 1, 3, 4, 7, 8, 9, 13, 14, 15, 16, 21, 22, 23, 24, 25, 31, 32, 33, 34, 35, 36, 43, 44, 45, 46, 47, 48, 49, 57, 58, 59, 60, 61, 62, 63, 64, 73, 74, 75, 76, 77, 78, 79, 80, 81, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 133, 134, 135 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) are the numbers satisfying m - 0.5 < sqrt(a(n)) <= m for some positive integer m. - Floor van Lamoen, Jul 24 2001 Lower s(n)-Wythoff sequence (as defined in A184117) associated to s(n) = A002024(n) = floor(1/2+sqrt(2n)), with complement (upper s(n)-Wythoff sequence) in A004202. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A061885(n-1)+1. - Franklin T. Adams-Watters, Jul 05 2009 a(n+1) - a(n) = A130296(n+1). - Reinhard Zumkeller, Jul 16 2008 a(A000217(n)) = n^2. - Reinhard Zumkeller, Feb 12 2011 a(n) = A004202(n)-A002024(n). - M. F. Hasler, Feb 13 2011 a(n) = n+A000217(A003056(n-1)) = n+A000217(A002024(n)-1). - M. F. Hasler, Feb 13 2011 a(n) = n + t(t+1)/2, where t = floor((-1+sqrt(8*n-7))/2). - Boris Putievskiy, Dec 13 2012 MATHEMATICA f[x_]:=Module[{c=1-x+x^2}, Range[c, c+x-1]]; Flatten[Array[f, 20]] (* Harvey P. Dale, Jul 31 2012 *) PROG (Haskell) a004201 n = a004201_list !! (n-1) a004201_list = f 1 [1..] where    f k xs = us ++ f (k + 1) (drop (k) vs) where (us, vs) = splitAt k xs -- Reinhard Zumkeller, Jun 20 2015, Feb 12 2011 (PARI) A004201(n)=n+(n=(sqrtint(8*n-7)+1)\2)*(n-1)\2  \\ M. F. Hasler, Feb 13 2011 CROSSREFS Cf. A004202, A007606. Sequence in context: A226227 A319736 A100452 * A109054 A129142 A075752 Adjacent sequences:  A004198 A004199 A004200 * A004202 A004203 A004204 KEYWORD nonn,nice AUTHOR Alexander Stasinski STATUS approved

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Last modified October 17 14:59 EDT 2019. Contains 328115 sequences. (Running on oeis4.)