login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069178 Centered 21-gonal numbers. 5
1, 22, 64, 127, 211, 316, 442, 589, 757, 946, 1156, 1387, 1639, 1912, 2206, 2521, 2857, 3214, 3592, 3991, 4411, 4852, 5314, 5797, 6301, 6826, 7372, 7939, 8527, 9136, 9766, 10417, 11089, 11782, 12496, 13231, 13987, 14764, 15562, 16381, 17221, 18082, 18964 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Ivan Panchenko, Table of n, a(n) for n = 1..1000

E. Weisstein, Centered Polygonal Numbers

Index entries for sequences related to centered polygonal numbers

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

FORMULA

a(n) = (21n^2 - 21n + 2)/2

a(n) = 21*n + a(n-1) - 21 (with a(1)=1). - Vincenzo Librandi, Aug 08 2010

G.f. -x*(1+19*x+x^2) / (x-1)^3. - R. J. Mathar, Feb 04 2011

Binomial transform of [1, 21, 21, 0, 0, 0,...] and Narayana transform (A001263) of [1, 21, 0, 0, 0,...]. - Gary W. Adamson, Jul 26 2011

a(n) = 1 + sum_{i=1..n} 21*(i-1). - Wesley Ivan Hurt, May 25 2013

MATHEMATICA

FoldList[#1 + #2 &, 1, 21 Range@ 45] (* Robert G. Wilson v, Feb 02 2011 *)

PROG

(PARI) a(n)=(21*n^2-21*n+2)/2 \\ Charles R Greathouse IV, Oct 07 2015

CROSSREFS

Cf. centered polygonal numbers listed in A069190.

Sequence in context: A221595 A051874 A140390 * A081929 A124715 A126376

Adjacent sequences:  A069175 A069176 A069177 * A069179 A069180 A069181

KEYWORD

easy,nonn

AUTHOR

Terrel Trotter, Jr., Apr 09 2002

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy .

Last modified August 24 04:58 EDT 2017. Contains 291052 sequences.