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 A238598 Largest integer k such that n >= k^2-k-1 = A165900(k). 1
 1, 1, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Also: Truncation to the integer part of the inverse function of A165900 = x -> x^2-x-1 (strictly increasing for x > 1/2): a(n) = floor(g(n)), where g = A165900^{-1}. A left inverse of A165900 on the positive integers: a(A165900(n)) = n for all n>0. LINKS FORMULA a(n) = A000194(n+2) - [n=1], where [P]=1 if P is true, [P]=0 else. PROG (PARI) A238598(n)=ceil(sqrtint(4*n+8)/2)-(n==1) CROSSREFS Sequence in context: A029836 A004257 A276611 * A156684 A070564 A072358 Adjacent sequences:  A238595 A238596 A238597 * A238599 A238600 A238601 KEYWORD nonn AUTHOR M. F. Hasler, Mar 01 2014 STATUS approved

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Last modified June 15 21:52 EDT 2021. Contains 345053 sequences. (Running on oeis4.)