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A213829
Principal diagonal of the convolution array A213828.
4
2, 28, 114, 296, 610, 1092, 1778, 2704, 3906, 5420, 7282, 9528, 12194, 15316, 18930, 23072, 27778, 33084, 39026, 45640, 52962, 61028, 69874, 79536, 90050, 101452, 113778, 127064, 141346, 156660, 173042
OFFSET
1,1
FORMULA
a(n) = 2*(n - 3*n^2 + 3*n^3).
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4).
G.f.: f(x)/g(x), where f(x) = 2*x*(1 + 10*x + 7*x^2) and g(x) = (1-x)^4.
MATHEMATICA
(See A213828.)
CROSSREFS
Cf. A213828.
Sequence in context: A281201 A051958 A123807 * A164834 A174707 A110241
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jul 04 2012
STATUS
approved