The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A381109

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A381109

a(n) = (21*n^2 + 9*n + 2)/2.
(history; published version)

#44 by Michael De Vlieger at Fri Mar 07 21:30:08 EST 2025

STATUS

reviewed

approved

#43 by Andrew Howroyd at Fri Mar 07 21:10:36 EST 2025

STATUS

proposed

reviewed

#42 by James C. McMahon at Fri Mar 07 11:43:43 EST 2025

STATUS

editing

proposed

#41 by James C. McMahon at Fri Mar 07 11:43:20 EST 2025

MATHEMATICA

LinearRecurrence[{3, -3, 1}, {1, 16, 52}, 4143] (* James C. McMahon, Mar 07 2025 *)

#40 by James C. McMahon at Fri Mar 07 11:41:09 EST 2025

MATHEMATICA

LinearRecurrence[{3, -3, 1}, {1, 16, 52}, 41] (* James C. McMahon, Mar 07 2025 *)

STATUS

approved

editing

#39 by N. J. A. Sloane at Fri Mar 07 09:15:32 EST 2025

STATUS

proposed

approved

#38 by Aaron David Fairbanks at Fri Mar 07 00:43:27 EST 2025

STATUS

editing

proposed

#37 by Aaron David Fairbanks at Fri Mar 07 00:42:15 EST 2025

COMMENTS

A 9-sided figure is obtained by truncating every other corner of a centered hexagonal figure as in A003215; a(n) is the number of dots in such a 9-sided figure with n+1 dots on each side.

STATUS

proposed

editing

Discussion

Fri Mar 07

00:43

Aaron David Fairbanks: Added explanation of the illustration in the comments.

#36 by Aaron David Fairbanks at Thu Mar 06 20:44:43 EST 2025

STATUS

editing

proposed

Discussion

Thu Mar 06

23:08

Kevin Ryde: Another term of illustration?  No.  You want something which defines.

23:09

Kevin Ryde: Dots were necessary in the past (and you'll even see program code made uun-runnable by leading dots).  They're not needed now, but 2 initial spaces is usual.

#35 by Aaron David Fairbanks at Thu Mar 06 20:40:04 EST 2025

EXAMPLE

1 16 52 109

Discussion

Thu Mar 06

20:40

Aaron David Fairbanks: Does it help to add another term?

20:44

Aaron David Fairbanks: By the way, the reason for the periods at the beginnings of lines was for consistency with other similar illustrations in the database, e.g. in A003215. Do you think they should be included?