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 A139593 A139276(n) followed by A139272(n+1). 9
 0, 3, 11, 22, 38, 57, 81, 108, 140, 175, 215, 258, 306, 357, 413, 472, 536, 603, 675, 750, 830, 913, 1001, 1092, 1188, 1287, 1391, 1498, 1610, 1725, 1845, 1968, 2096, 2227, 2363, 2502, 2646, 2793, 2945, 3100, 3260, 3423, 3591, 3762 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Sequence found by reading the line from 0, in the direction 0, 3,... and the same line from 0, in the direction 0, 11,..., in the square spiral whose vertices are the triangular numbers A000217. A139593 appears (both numerically and via back of an envelope algebra, but not a publishable proof) to be the cumulative sum of A047470. - Markus J. Q. Roberts, Jul 12 2009 LINKS Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1). FORMULA Array read by rows: row n gives 8*n^2 + 3n, 8*(n+1)^2 - 5(n+1). a(n) = (-1+(-1)^n+6*n+8*n^2)/4. a(n) = 2*a(n-1)-2*a(n-3)+a(n-4). G.f.: -x*(5*x+3) / ((x-1)^3*(x+1)). - Colin Barker, Sep 15 2013 EXAMPLE Array begins: 0, 3 11, 22 38, 57 81, 108 MATHEMATICA LinearRecurrence[{2, 0, -2, 1}, {0, 3, 11, 22}, 50] (* Harvey P. Dale, Feb 09 2019 *) CROSSREFS Cf. A000217, A046092, A139272, A139276, A077221, A139591, A139592, A139594, A139595, A139596, A139597, A139598, A047470. Sequence in context: A240371 A158653 A129215 * A121471 A293766 A178946 Adjacent sequences:  A139590 A139591 A139592 * A139594 A139595 A139596 KEYWORD easy,nonn AUTHOR Omar E. Pol, May 03 2008 EXTENSIONS Edited by Omar E. Pol, Jul 13 2009 STATUS approved

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Last modified January 28 03:28 EST 2020. Contains 331314 sequences. (Running on oeis4.)