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 A033551 Closest integer to (Pi/4)*n^2. 1
 1, 3, 7, 13, 20, 28, 38, 50, 64, 79, 95, 113, 133, 154, 177, 201, 227, 254, 284, 314, 346, 380, 415, 452, 491, 531, 573, 616, 661, 707, 755, 804, 855, 908, 962, 1018, 1075, 1134, 1195, 1257, 1320, 1385, 1452, 1521 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 FORMULA a(n) = round( (Pi/4) * n^2 ). EXAMPLE a(3)=7, since 3^2*Pi/4 = 7.06858347. MAPLE seq(round((1/4)*Pi*n^2), n = 1..50); # G. C. Greubel, Oct 12 2019 MATHEMATICA Round[Pi/4 Range[50]^2] (* Harvey P. Dale, May 11 2016 *) PROG (PARI) a(n) = round((Pi/4) * n^2); \\ Michel Marcus, Sep 02 2013 (MAGMA) R:= RealField(20); [Round(Pi(R)*n^2/4): n in [1..50]]; // G. C. Greubel, Oct 12 2019 (Sage) [round(pi*n^2/4) for n in (1..50)] # G. C. Greubel, Oct 12 2019 (GAP) List([1..50], n-> Int(Round(Atan(1.0)*n^2)) ); # G. C. Greubel, Oct 12 2019 CROSSREFS Approximation for A051233. Sequence in context: A310266 A014283 A294398 * A022777 A033154 A076950 Adjacent sequences:  A033548 A033549 A033550 * A033552 A033553 A033554 KEYWORD easy,nonn,changed AUTHOR Joe K. Crump (joecr(AT)carolina.rr.com) STATUS approved

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Last modified October 21 14:04 EDT 2019. Contains 328299 sequences. (Running on oeis4.)