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A213839
Principal diagonal of the convolution array A213838.
3
1, 20, 89, 240, 505, 916, 1505, 2304, 3345, 4660, 6281, 8240, 10569, 13300, 16465, 20096, 24225, 28884, 34105, 39920, 46361, 53460, 61249, 69760, 79025, 89076, 99945, 111664, 124265, 137780, 152241, 167680
OFFSET
1,2
FORMULA
a(n) = (8*n - 21*n^2 + 16*n^3)/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) = x*(1 + 16*x + 15*x^2) and g(x) = (1-x)^4.
MATHEMATICA
(See A213838.)
LinearRecurrence[{4, -6, 4, -1}, {1, 20, 89, 240}, 40] (* Harvey P. Dale, Mar 10 2013 *)
CROSSREFS
Cf. A213838.
Sequence in context: A306987 A249983 A234258 * A264302 A220200 A242656
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jul 05 2012
STATUS
approved