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A172045
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a(n) = (9*n^4+10*n^3-3*n^2-4*n)/12.
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1
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0, 1, 17, 80, 240, 565, 1141, 2072, 3480, 5505, 8305, 12056, 16952, 23205, 31045, 40720, 52496, 66657, 83505, 103360, 126560, 153461, 184437, 219880, 260200, 305825, 357201, 414792, 479080, 550565, 629765, 717216, 813472, 919105, 1034705
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OFFSET
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0,3
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COMMENTS
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The sequence is related to A002414 (octagonal pyramidal numbers) by a(n) = n*A002414(n)-sum(A002414(i), i=1..n-1) for n>0.
This is the case d=3 in the identity n*(n*(n+1)*(2*d*n-2*d+3)/6)-sum(k*(k+1)*(2*d*k-2*d+3)/6, k=0..n-1) = n*(n+1)*(3*d*n^2-d*n+4*n-2*d+2)/12. - Bruno Berselli, Nov 03 2010
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LINKS
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B. Berselli, A description of the recursive method in Comments lines: website Matem@ticamente (in Italian).
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FORMULA
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G.f. -x*(1 +12*x +5*x^2) / (x - 1)^5 . - R. J. Mathar, Nov 17 2011
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MATHEMATICA
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CoefficientList[Series[x (1 + 12 x + 5 x^2)/(1 - x)^5, {x, 0, 40}], x] (* Vincenzo Librandi, Jan 01 2014 *)
LinearRecurrence[{5, -10, 10, -5, 1}, {0, 1, 17, 80, 240}, 40] (* Harvey P. Dale, Aug 25 2019 *)
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PROG
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(Magma) [(9*n^4+10*n^3-3*n^2-4*n)/12: n in [0..50]]; // Vincenzo Librandi, Jan 01 2014
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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