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 A195058 Concentric 23-gonal numbers. 7
 0, 1, 23, 47, 92, 139, 207, 277, 368, 461, 575, 691, 828, 967, 1127, 1289, 1472, 1657, 1863, 2071, 2300, 2531, 2783, 3037, 3312, 3589, 3887, 4187, 4508, 4831, 5175, 5521, 5888, 6257, 6647, 7039, 7452, 7867, 8303, 8741, 9200, 9661, 10143, 10627 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Ivan Panchenko, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1). FORMULA a(n) = 23*n^2/4 + 19*((-1)^n-1)/8. From Colin Barker, Sep 16 2012: (Start) a(n) = 2*a(n-1) - 2*a(n-3) + a(n-4). G.f.: x*(1 + 21*x + x^2)/((1-x)^3*(1+x)). (End) MATHEMATICA Table[23n^2/4 + 19((-1)^n - 1)/8, {n, 0, 49}] (* Alonso del Arte, Jan 23 2015 *) PROG (PARI) a(n)=23*n^2/4+19*((-1)^n-1)/8 \\ Charles R Greathouse IV, Oct 07 2015 CROSSREFS Column 23 of A195040. Cf. A032527, A032528, A195049, A195149, A195158. Sequence in context: A090191 A281022 A054821 * A039374 A043197 A043977 Adjacent sequences:  A195055 A195056 A195057 * A195059 A195060 A195061 KEYWORD nonn,easy AUTHOR Omar E. Pol, Sep 28 2011 STATUS approved

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Last modified July 26 10:48 EDT 2021. Contains 346294 sequences. (Running on oeis4.)