login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A152773 3 times heptagonal numbers: a(n) = 3n(5n-3)/2. 16
0, 3, 21, 54, 102, 165, 243, 336, 444, 567, 705, 858, 1026, 1209, 1407, 1620, 1848, 2091, 2349, 2622, 2910, 3213, 3531, 3864, 4212, 4575, 4953, 5346, 5754, 6177, 6615, 7068, 7536, 8019, 8517, 9030, 9558, 10101, 10659, 11232, 11820 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Also the number of 6-cycles in the (n+5)-triangular honeycomb acute knight graph. - Eric W. Weisstein, Jun 25 2017

LINKS

Ivan Panchenko, Table of n, a(n) for n = 0..1000

Eric Weisstein's World of Mathematics, Graph Cycle

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

a(n) = (15n^2 - 9n)/2 = A000566(n)*3.

a(n) = a(n-1)+15*n-12 with n>0, a(0)=0. - Vincenzo Librandi, Nov 26 2010

G.f.: 3*x*(1+4*x)/(1-x)^3. - Bruno Berselli, Jan 21 2011

a(0)=0, a(1)=3, a(2)=21, a(n)=3*a(n-1)-3*a(n-2)+a(n-3). - Harvey P. Dale, May 08 2012

a(n) = n + A226489(n). - Bruno Berselli, Jun 11 2013

MATHEMATICA

Table[3 n (5 n - 3)/2, {n, 0, 50}] (* Harvey P. Dale, May 08 2012 *)

LinearRecurrence[{3, -3, 1}, {0, 3, 21}, 50] (* Harvey P. Dale, May 08 2012 *)

CoefficientList[Series[-((3 x^5 (1 + 4 x))/(-1 + x)^3), {x, 0, 20}], x] (* Eric W. Weisstein, Jun 25 2017 *)

PROG

(PARI) a(n)=3*n*(5*n-3)/2 \\ Charles R Greathouse IV, Sep 24 2015

CROSSREFS

Cf. A000566, A135706.

3 times n-gonal numbers: A045943, A033428, A062741, A094159, A152751, A152759, A152767, A153783, A153448, A153875.

Cf. numbers of the form n*(n*k-k+6))/2, this sequence is the case k=15: see Comments lines of A226492.

Cf. A002378 (3-cycles in triangular honeycomb acute knight graph), A045943 (4-cycles), A028896 (5-cycles).

Sequence in context: A027499 A303834 A340687 * A039595 A033567 A181156

Adjacent sequences: A152770 A152771 A152772 * A152774 A152775 A152776

KEYWORD

nonn,easy

AUTHOR

Omar E. Pol, Dec 13 2008

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 6 15:33 EST 2022. Contains 358644 sequences. (Running on oeis4.)