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 A096129 Middle term of a triple of consecutive numbers which are sums of two squares. 0
 1, 9, 73, 289, 801, 1801, 3529, 6273, 10369, 16201, 24201, 34849, 48673, 66249, 88201, 115201, 147969, 187273, 233929, 288801, 352801, 426889, 512073, 609409, 720001, 845001, 985609, 1143073, 1318689, 1513801, 1729801, 1968129, 2230273 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1). FORMULA a(n)=8*A000537(n) + 1. a(n)=1+2*n^2+4*n^3+2*n^4. G.f.: -(x^4+4*x^3+38*x^2+4*x+1)/(x-1)^5. [Colin Barker, Jul 28 2012] EXAMPLE 1801 is in the sequence because we may for instance write 1800 = 6^2 + 42^2; 1801 = 24^2 + 35^2; 1802 = 29^2 + 31^2. MATHEMATICA LinearRecurrence[{5, -10, 10, -5, 1}, {1, 9, 73, 289, 801}, 40] (* Harvey P. Dale, Oct 22 2019 *) CROSSREFS Cf. A001481. Sequence in context: A043079 A099973 A091986 * A291700 A143571 A244202 Adjacent sequences:  A096126 A096127 A096128 * A096130 A096131 A096132 KEYWORD nonn,easy AUTHOR Lekraj Beedassy, Jul 23 2004 EXTENSIONS Corrected and extended by Ray Chandler, Jul 29 2004 STATUS approved

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Last modified January 23 11:42 EST 2022. Contains 350512 sequences. (Running on oeis4.)