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 A056520 (n+2)*(2*n^2-n+3)/6. 19
 1, 2, 6, 15, 31, 56, 92, 141, 205, 286, 386, 507, 651, 820, 1016, 1241, 1497, 1786, 2110, 2471, 2871, 3312, 3796, 4325, 4901, 5526, 6202, 6931, 7715, 8556, 9456, 10417, 11441, 12530, 13686, 14911, 16207, 17576, 19020, 20541, 22141, 23822 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) = A000330(n)+1. Hankel transform of A030238. - Paul Barry, Oct 16 2007 Equals (1, 2, 3, 4, 5,...) convolved with (1, 0, 3, 5, 7, 9,...). - Gary W. Adamson, Jul 31 2010 a(n) equals n!^2 times the determinant of the n X n matrix whose (i,j)-entry is 1 + KroneckerDelta[i, j] (-1 + (1 + i^2)/i^2). - John M. Campbell, May 20 2011 Let b(0)=b(1)=1, b(n)=max(b(n-1)+(n-1)^2,b(n-2)+(n-2)^2); then A056520(n)=b(n+1). - Yalcin Aktar, Jul 28 2011 Positions of ones in A253903. - Harvey P. Dale, Mar 05 2015 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Guo-Niu Han, Enumeration of Standard Puzzles\Guo-Niu Han, Enumeration of Standard Puzzles [Cached copy] Amit Kumar Singh, Akash Kumar and Thambipillai Srikanthan, Accelerating Throughput-aware Run-time Mapping for Heterogeneous MPSoCs, ACM Transactions on Design Automation of Electronic Systems, 2012. - From N. J. A. Sloane, Dec 25 2012 FORMULA a(n) = a(n-1)+n^2. G.f.: (1-2*x+4*x^2-x^3)/(1-x)^4. - Paul Barry, Apr 14 2010 MATHEMATICA a[n_] := (n+2)*(2*n^2-n+3)/6; Table[a[n], {n, 0, 100}] (* Vladimir Joseph Stephan Orlovsky, Dec 17 2008 *) s = 1; lst = {s}; Do[s += n^2; AppendTo[lst, s], {n, 1, 41, 1}]; lst (* Zerinvary Lajos, Jul 12 2009 *) Table[n!^2*Det[Array[KroneckerDelta[#1, #2](((#1^2+1)/(#1^2))-1)+1&, {n, n}]], {n, 1, 20}] (* John M. Campbell, May 20 2011 *) FoldList[#1 + #2^2 &, 1, Range@ 40] (* Robert G. Wilson v, Oct 28 2011 *) PROG (MAGMA)[(n+2)*(2*n^2-n+3)/6: n in [0..40]]; // Vincenzo Librandi, May 24 2011 (PARI) a(n)=(n+2)*(2*n^2-n+3)/6 \\ Charles R Greathouse IV, Jul 02 2013 CROSSREFS Cf. A253903. Sequence in context: A236111 A230455 A141126 * A289961 A290068 A289935 Adjacent sequences:  A056517 A056518 A056519 * A056521 A056522 A056523 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Laura Kasavan (maui12129(AT)cswebmail.com), Aug 26 2000 STATUS approved

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