The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A221920 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A221920

a(n) = 3*n/gcd(3*n, n+3), n >= 3.
(history; published version)

#31 by Michel Marcus at Mon Oct 09 02:20:40 EDT 2023

STATUS

reviewed

approved

#30 by Joerg Arndt at Mon Oct 09 01:55:08 EDT 2023

STATUS

proposed

reviewed

#29 by Amiram Eldar at Mon Oct 09 01:44:41 EDT 2023

STATUS

editing

proposed

#28 by Amiram Eldar at Mon Oct 09 01:28:57 EDT 2023

FORMULA

Sum_{k=3..n} a(k) ~ (61/54) * n^2. - Amiram Eldar, Oct 09 2023

MATHEMATICA

a[n_] := 3*n/GCD[3*n, n+3]; Array[a, 63, 3] (* Amiram Eldar, Oct 09 2023 *)

#27 by Amiram Eldar at Mon Oct 09 01:28:40 EDT 2023

FORMULA

G.f.: -x^3*(6*x^17 + 3*x^16 - 3*x^14 - 6*x^13 - x^12 - 12*x^11 - 15*x^10 - 6*x^9 - 33*x^8 - 30*x^7 - 9*x^6 - 24*x^5 - 21*x^4 - 2*x^3 - 15*x^2 - 12*x - 3) / ((x-1)^2*(x^2 + x + 1)^2*(x^6 + x^3 + 1)^2). [_- _Colin Barker_, Feb 25 2013]

STATUS

approved

editing

#26 by Joerg Arndt at Mon Oct 21 02:21:38 EDT 2019

STATUS

proposed

approved

#25 by Michel Marcus at Mon Oct 21 01:05:59 EDT 2019

STATUS

editing

proposed

#24 by Michel Marcus at Mon Oct 21 01:05:36 EDT 2019

LINKS

<a href="/index/Rec#order_18">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,-1).

STATUS

proposed

editing

#23 by Jon E. Schoenfield at Sun Oct 20 22:33:58 EDT 2019

STATUS

editing

proposed

#22 by Jon E. Schoenfield at Sun Oct 20 22:33:56 EDT 2019

NAME

a(n) = 3*n/gcd(3*n, n+3), n >= 3.

FORMULA

G.f.: -x^3*(6*x^17 + 3*x^16 - 3*x^14 - 6*x^13 - x^12 - 12*x^11 - 15*x^10 - 6*x^9 - 33*x^8 - 30*x^7 - 9*x^6 - 24*x^5 - 21*x^4 - 2*x^3 - 15*x^2 - 12*x - 3) / ((x -1)^2*(x^2 + x + 1)^2*(x^6 + x^3 + 1)^2). [Colin Barker, Feb 25 2013]

STATUS

approved

editing