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 A143051 Smallest number not occurring earlier and smaller than the largest square so far, the next square if no such number exists. 5
 0, 1, 4, 2, 3, 9, 5, 6, 7, 8, 16, 10, 11, 12, 13, 14, 15, 25, 17, 18, 19, 20, 21, 22, 23, 24, 36, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 49, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 64, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 81, 65, 66, 67, 68, 69, 70, 71 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Permutation of the natural numbers, inverse: A143052; A143053(n) = a(a(n)); a(A000290(n)) = A005563(n-1); a(A002522(n)) = A000290(n+1); for n>1: GCD(a(n^2),a(n^2+1)) = A050873(A000290(n),A002522(n)) = A022998(n+1). LINKS Peter Kagey, Table of n, a(n) for n = 0..10000 FORMULA a(n) = if n=0 then 0 else if n=1+k^2 then n+2*k else n-1. CROSSREFS Sequence in context: A201651 A026246 A321122 * A297022 A282888 A278101 Adjacent sequences:  A143048 A143049 A143050 * A143052 A143053 A143054 KEYWORD nonn AUTHOR Reinhard Zumkeller, Jul 20 2008 STATUS approved

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Last modified June 21 10:02 EDT 2021. Contains 345358 sequences. (Running on oeis4.)