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A085611
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Difference between A007678(2n)/(2n) and (n-1)^2.
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1
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0, 0, 0, 1, 6, 12, 32, 57, 73, 144, 210, 255, 394, 516, 520, 833, 1032, 1182, 1518, 1809, 1927, 2500, 2904, 3205, 3836, 4368, 4768, 5577, 6258, 6550, 7780, 8625, 9265, 10496, 11526, 12403, 13782, 15012, 15996, 17689, 19140, 20218, 22274, 23961, 25309, 27588, 29532, 31209, 33688
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OFFSET
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1,5
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COMMENTS
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If we define b(n) by b(n)=local(nr,fn,cn); nr=0; fn=floor(n/2); cn=ceiling(n/2); forstep (i=n,4,-2,nr=nr+(i-2)*fn+(i-4)*cn); nr then a(n) is given by (A007678(2n)-b(2n))/(2n).
This b(n) is given by (n-2)*(2*n^2 - 4*n + 3*(-1)^n - 3)/8 for n > 1. - R. J. Mathar, Oct 18 2013
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LINKS
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Table of n, a(n) for n=1..49.
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FORMULA
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a(n) = A007678(2*n)/(2*n) - (n-1)^2. - M. F. Hasler, Aug 06 2021
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PROG
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(PARI) apply( {A085611(n)=A007678(2*n)/(2*n)-(n-1)^2}, [1..40]) \\ M. F. Hasler, Aug 05 2021
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CROSSREFS
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Cf. A007678, A006533, A000290.
Sequence in context: A096356 A065992 A263587 * A122608 A268283 A196992
Adjacent sequences: A085608 A085609 A085610 * A085612 A085613 A085614
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KEYWORD
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nonn
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AUTHOR
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Jon Perry, Jul 08 2003
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EXTENSIONS
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The last term seemed to be corrupted and has now been deleted. - N. J. A. Sloane, Oct 29 2006
Edited and more terms from M. F. Hasler, Aug 06 2021
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STATUS
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approved
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