The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A002717 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A002717

a(n) = floor(n(n+2)(2n+1)/8).
(history; published version)

#118 by Alois P. Heinz at Fri Jun 09 03:17:20 EDT 2023

STATUS

editing

approved

#117 by Alois P. Heinz at Fri Jun 09 03:17:17 EDT 2023

DATA

0, 1, 5, 13, 27, 48, 78, 118, 170, 235, 315, 411, 525, 658, 812, 988, 1188, 1413, 1665, 1945, 2255, 2596, 2970, 3378, 3822, 4303, 4823, 5383, 5985, 6630, 7320, 8056, 8840, 9673, 10557, 11493, 12483, 13528, 14630, 15790, 17010, 18291, 19635, 21043, 22517, 24058

STATUS

approved

editing

#116 by Joerg Arndt at Thu Mar 23 06:52:05 EDT 2023

STATUS

editing

approved

#115 by Joerg Arndt at Thu Mar 23 06:51:57 EDT 2023

FORMULA

a(n) = (w(w+1)(4w-3(-1)^n+2)+n(n+1)(n+2))/6, with w:=floor(n/2) - Steve Warson, Mar 21 2023

#114 by Alois P. Heinz at Tue Mar 21 12:33:42 EDT 2023

STATUS

proposed

editing

Discussion

Wed Mar 22

02:33

Jon E. Schoenfield: This seems like an obfuscation to me.

#113 by Michel Marcus at Tue Mar 21 12:21:37 EDT 2023

STATUS

editing

proposed

Discussion

Tue Mar 21

12:33

Alois P. Heinz: I do not see the point ...

#112 by Michel Marcus at Tue Mar 21 12:21:06 EDT 2023

FORMULA

a(n) = Sum_{i=1..n} T(n-i+1)+T(n-2*i+1), where T(n)=n*(n+1)/2=A000217(n) if n>0 and 0 if n<=0. So we have a(n+2)-a(n)=(n+2)^2+(n+1)*(n+2)/2. - Maurice Mischler, Sep 08 2014

STATUS

proposed

editing

#111 by Michel Marcus at Tue Mar 21 12:18:11 EDT 2023

STATUS

editing

proposed

#110 by Michel Marcus at Tue Mar 21 12:17:55 EDT 2023

FORMULA

G.f. : a(n) = (w(w+1)(4w-3(-1)^n+2)+n(n+1)(n+2))/6, with w:=floor(n/2) - Steve Warson 03/, Mar 21/ 2023

STATUS

proposed

editing

Discussion

Tue Mar 21

12:18

Michel Marcus: fixed formula and date formats

#109 by Steve Warson at Tue Mar 21 10:38:14 EDT 2023

STATUS

editing

proposed

Discussion

Tue Mar 21

11:28

Joerg Arndt: (not a g.f. and) more complicated than the formula given in name, so what is the point?