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 A080037 a(0)=2; for n > 0, a(n) = n + floor(sqrt(4n-3)) + 2. 19
 2, 4, 6, 8, 9, 11, 12, 14, 15, 16, 18, 19, 20, 22, 23, 24, 25, 27, 28, 29, 30, 32, 33, 34, 35, 36, 38, 39, 40, 41, 42, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68, 69, 70, 71, 72, 74, 75, 76, 77, 78, 79, 80, 81, 83, 84, 85, 86, 87, 88, 89, 90, 92 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS a(0)=2, a(1)=4; for n > 2, a(n) = a(n-1) + 1 if n is already in the sequence, a(n) = a(n-1) + 2 otherwise. [corrected by Jon E. Schoenfield, Jun 24 2018] For n > 0, a(n) = ceiling((1 + sqrt(n))^2). Empirical observation. - Ronald S. Tiberio, Jun 24 2018 For n > 0, a(n) is the minimal number of thumbtacks needed to secure n square sheets of paper on a bulletin board - one thumbtack in each corner of each sheet - slight overlap allowed so that one thumbtack can secure up to four sheets. - Ronald S. Tiberio, Jun 24 2018 LINKS B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, J. Integer Seqs., Vol. 6 (2003), #03.2.2. B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, arXiv:math/0305308 [math.NT], 2003. CROSSREFS Cf. A000267, A080036. Sequence in context: A217352 A036627 A191982 * A184012 A186354 A186149 Adjacent sequences:  A080034 A080035 A080036 * A080038 A080039 A080040 KEYWORD nonn AUTHOR N. J. A. Sloane, Mar 14 2003 STATUS approved

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Last modified July 18 21:23 EDT 2018. Contains 312765 sequences. (Running on oeis4.)