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 A112087 4*(n^2 - n + 1). 4
 4, 12, 28, 52, 84, 124, 172, 228, 292, 364, 444, 532, 628, 732, 844, 964, 1092, 1228, 1372, 1524, 1684, 1852, 2028, 2212, 2404, 2604, 2812, 3028, 3252, 3484, 3724, 3972, 4228, 4492, 4764, 5044, 5332, 5628, 5932, 6244, 6564, 6892, 7228, 7572, 7924, 8284 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Diagonal of a number spiral. LINKS Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA Equals 4*A002061. - Robert G. Wilson v a(n) = 8*n + a(n-1) - 8 (with a(1)=4). - Vincenzo Librandi, Nov 13 2010 EXAMPLE ..43.44.45.46.47.48.49.50... ..42.21.22.23.24.25.26.51... ..40.19..7..8..9.10.27.52... ..40.19..6..1..2.11.28.... ..39.18..5..4..3.12.29 ..38.17.16.15.14.13.30 ..37.36.35.34.33.32.31 MATHEMATICA Table[4(n^2 - n + 1), {n, 2, 47}] (* Robert G. Wilson v *) PROG (Maxima) makelist(4*n^2 - 4*n + 4, n, 1, 55); /* Martin Ettl, Oct 16 2012 */ (PARI) a(n)=4*(n^2-n+1) \\ Charles R Greathouse IV, Jun 17 2017 CROSSREFS Sequence in context: A278211 A192736 A109629 * A166019 A184633 A006000 Adjacent sequences:  A112084 A112085 A112086 * A112088 A112089 A112090 KEYWORD nonn,easy AUTHOR Jenny X. Chen (pookahead(AT)gmail.com), Nov 28 2005 EXTENSIONS Edited and extended by Robert G. Wilson v, Nov 29 2005 STATUS approved

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Last modified December 12 13:56 EST 2018. Contains 318063 sequences. (Running on oeis4.)