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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A158056 a(n) = 16*n^2 + 2*n. 2
18, 68, 150, 264, 410, 588, 798, 1040, 1314, 1620, 1958, 2328, 2730, 3164, 3630, 4128, 4658, 5220, 5814, 6440, 7098, 7788, 8510, 9264, 10050, 10868, 11718, 12600, 13514, 14460, 15438, 16448, 17490, 18564, 19670, 20808, 21978, 23180, 24414, 25680 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The identity (16*n + 1)^2 - (16*n^2 + 2*n)*4^2 = 1 can be written as A158057(n)^2 - a(n)*4^2 = 1. - Vincenzo Librandi, Feb 09 2012

Sequence found by reading the line from 18, in the direction 18, 68, ... in the square spiral whose vertices are the generalized decagonal numbers A074377. - Omar E. Pol, Nov 02 2012

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

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

FORMULA

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).

G.f.: 2*x*(-9 - 7*x)/(x-1)^3.

MATHEMATICA

LinearRecurrence[{3, -3, 1}, {18, 68, 150}, 50]

Table[16n^2+2n, {n, 40}]  (* Harvey P. Dale, Apr 13 2011 *)

PROG

(MAGMA) I:=[18, 68, 150]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]];

(PARI) a(n) = 16*n^2 + 2*n.

CROSSREFS

Cf. A158057.

Sequence in context: A143859 A063523 A045234 * A304061 A214491 A135470

Adjacent sequences:  A158053 A158054 A158055 * A158057 A158058 A158059

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Mar 12 2009

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 24 04:00 EDT 2019. Contains 322406 sequences. (Running on oeis4.)