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A213832
Principal diagonal of the convolution array A213831.
3
1, 19, 78, 202, 415, 741, 1204, 1828, 2637, 3655, 4906, 6414, 8203, 10297, 12720, 15496, 18649, 22203, 26182, 30610, 35511, 40909, 46828, 53292, 60325, 67951, 76194, 85078, 94627, 104865, 115816, 127504
OFFSET
1,2
FORMULA
G.f.: x*(1 + 15*x + 8*x^2)/(1-x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4).
a(n) = (n - 7*n^2 + 8*n^3)/2.
a(n) = Sum_{i = 0..n-1} (n + i)*(n + 3*i). - Bruno Berselli, Feb 14 2018
MATHEMATICA
(See A213831.)
CROSSREFS
Cf. A213831.
Sequence in context: A304513 A041698 A041700 * A350194 A372757 A132234
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jul 04 2012
STATUS
approved