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 A139592 A033585(n) followed by A139271(n+1). 9
 0, 2, 10, 20, 36, 54, 78, 104, 136, 170, 210, 252, 300, 350, 406, 464, 528, 594, 666, 740, 820, 902, 990, 1080, 1176, 1274, 1378, 1484, 1596, 1710, 1830, 1952, 2080, 2210, 2346, 2484, 2628, 2774, 2926, 3080, 3240, 3402, 3570, 3740 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Sequence found by reading the line from 0, in the direction 0, 2,... and the same line from 0, in the direction 0, 10,..., in the square spiral whose vertices are the triangular numbers A000217. a(n) = 2*A006578(n) - A002378(n)/2 = 2*A035608(n). [From Reinhard Zumkeller, Feb 07 2010] 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 + 2n, 8*(n+1)^2 - 6(n+1). a(n) = 2*floor((n + 1/4)^2). [From Reinhard Zumkeller, Feb 07 2010] G.f.: 2*x*(1+3*x)/((1-x)^3*(1+x)). [Colin Barker, Apr 26 2012] EXAMPLE Array begins: 0, 2 10, 20 36, 54 78, 104 CROSSREFS Cf. A000217, A033585, A046092, A139271, A077221, A139591, A139593, A139595, A139596, A139597, A139598. Sequence in context: A305448 A177150 A165551 * A294544 A285104 A120552 Adjacent sequences:  A139589 A139590 A139591 * A139593 A139594 A139595 KEYWORD easy,nonn AUTHOR Omar E. Pol, May 03 2008 STATUS approved

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Last modified December 8 01:59 EST 2019. Contains 329850 sequences. (Running on oeis4.)