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 A126665 a(n) = -n^2 + 9n + 53. 5
 53, 61, 67, 71, 73, 73, 71, 67, 61, 53, 43, 31, 17, 1, -17, -37, -59, -83, -109, -137, -167, -199, -233, -269, -307, -347, -389, -433, -479, -527, -577, -629, -683, -739, -797, -857, -919, -983, -1049, -1117, -1187, -1259, -1333, -1409, -1487, -1567, -1649, -1733, -1819, -1907, -1997, -2089, -2183, -2279 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Quadratic equation derived from the four primes 61, 67, 71, 73 using the method of common differences. Many of the initial terms are primes. LINKS Michael M. Ross, Natural Numbers Robert Sacks, Number Spiral: Method of Common Differences Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA From Arkadiusz Wesolowski, Oct 24 2013: (Start) a(n) = - A186950(n+19). G.f.: (53 - 98*x + 43*x^2)/(1 - x)^3. (End) EXAMPLE For n=8, -1*8^2 + 9*8 + 53 = 61. MATHEMATICA Table[ - n^2 + 9*n + 53, {n, 0, 46}] (* Arkadiusz Wesolowski, Oct 24 2013 *) PROG (PARI) a(n) = -n^2 + 9*n + 53 \\ Michel Marcus, Jun 30 2013 (MAGMA) [-n^2+9*n+53 : n in [0..46]]; // Arkadiusz Wesolowski, Oct 24 2013 CROSSREFS Sequence in context: A180553 A079593 A086082 * A279191 A107160 A075587 Adjacent sequences:  A126662 A126663 A126664 * A126666 A126667 A126668 KEYWORD sign,easy AUTHOR Michael M. Ross, Mar 13 2007 STATUS approved

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Last modified August 18 15:00 EDT 2019. Contains 326106 sequences. (Running on oeis4.)