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0, 15, 35, 60, 90, 125, 165, 210, 260, 315, 375, 440, 510, 585, 665, 750, 840, 935, 1035, 1140, 1250, 1365, 1485, 1610, 1740, 1875, 2015, 2160, 2310, 2465, 2625, 2790, 2960, 3135, 3315, 3500, 3690, 3885, 4085, 4290, 4500, 4715, 4935, 5160, 5390, 5625, 5865
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OFFSET
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0,2
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COMMENTS
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Numbers of the form n*t(n+5,h)-(n+5)*t(n,h), where t(k,h) = k(k+2h+1)/2 for any h. Likewise:
A000217(n) = n*t(n+1,h)-(n+1)*t(n,h),
A005563(n) = n*t(n+2,h)-(n+2)*t(n,h),
A140091(n) = n*t(n+3,h)-(n+3)*t(n,h),
A067728(n) = n*t(n+4,h)-(n+4)*t(n,h) (n>0),
A140681(n) = n*t(n+6,h)-(n+6)*t(n,h).
Also, a(k) is a square for k = (5/2)*(A078986(n)-1).
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LINKS
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Bruno Berselli, Table of n, a(n) for n = 0..1000
Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
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G.f.: 5*x*(3-2*x)/(1-x)^3.
a(n) = a(-n-5) = 5*A055998(n).
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MATHEMATICA
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Table[(5/2) n (n + 5), {n, 0, 46}]
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PROG
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(MAGMA) [5*n*(n+5)/2: n in [0..46]];
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CROSSREFS
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Cf. A000217, A005563, A067728, A140091, A140681.
Sequence in context: A187400 A162280 A063532 * A067930 A146688 A146656
Adjacent sequences: A212328 A212329 A212330 * A212332 A212333 A212334
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KEYWORD
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nonn,easy
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AUTHOR
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Bruno Berselli, May 30 2012
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STATUS
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approved
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