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A108766
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A007290(n+2) - 1 = 2*C(n+2,3) - 1.
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1
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-1, 1, 7, 19, 39, 69, 111, 167, 239, 329, 439, 571, 727, 909, 1119, 1359, 1631, 1937, 2279, 2659, 3079, 3541, 4047, 4599, 5199, 5849, 6551, 7307, 8119, 8989, 9919, 10911, 11967, 13089, 14279, 15539, 16871, 18277, 19759, 21319, 22959, 24681, 26487, 28379, 30359, 32429, 34591, 36847, 39199, 41649
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Note (in reference to program code): 1kbasejrokseq = A005286 (Number of permutations of [n+3] with three inversions.), 1ibasekrokseq = A004006 = C(n,1)+C(n,2)+C(n,3) (from second term)
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FORMULA
| a(n) = n*(n+2)*(n+1)/3 - 1, G.f. (-1+5*x-3*x^2+x^3)/(x-1)^4
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MAPLE
| a[0]:=-1:a[1]:=1:for n from 2 to 50 do a[n]:=a[n-1]+n^2+n od: seq(a[n], n=0..49); .
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MATHEMATICA
| s1=s2=s3=s4=0; lst={}; Do[a=n+(n+2); s1+=a; s2+=s1; s3+=s2; s4+=s3; AppendTo[lst, s2-1], {n, 0, 5!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 04 2009]
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PROG
| Floretion Algebra Multiplication Program, FAMP Code: a(n) = -1tesrok[(- 'j + 'k - 'ii' - 'ij' - 'ik')(- 'i + 'j - 'kk' - 'ki' - 'kj'), Roktype: Y[sqa.Findk()] = Y[sqa.Findk()] + p (internal program code).
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CROSSREFS
| Cf. A007290, A005286, A004006.
Sequence in context: A152728 A099061 A078163 * A120720 A098422 A191066
Adjacent sequences: A108763 A108764 A108765 * A108767 A108768 A108769
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KEYWORD
| easy,sign
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AUTHOR
| Creighton Dement (creighton.k.dement(AT)uni-oldenburg.de), Jun 24 2005
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