login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A153785 5 times heptagonal numbers: a(n) = 5*n*(5*n-3)/2. 2
0, 5, 35, 90, 170, 275, 405, 560, 740, 945, 1175, 1430, 1710, 2015, 2345, 2700, 3080, 3485, 3915, 4370, 4850, 5355, 5885, 6440, 7020, 7625, 8255, 8910, 9590, 10295, 11025, 11780, 12560, 13365, 14195, 15050, 15930, 16835, 17765 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

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

FORMULA

a(n) = (25*n^2 - 15*n)/2 = A000566(n)*5.

a(n) = 25*n + a(n-1) - 20 (with a(0)=0). - Vincenzo Librandi, Aug 03 2010

From G. C. Greubel, Aug 28 2016: (Start)

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

G.f.: 5*x*(1 + 4*x))/(1 - x)^3.

E.g.f.: (5/2)*x*(2 + 5*x)*exp(x). (End)

MATHEMATICA

s=0; lst={s}; Do[s+=n; AppendTo[lst, s], {n, 5, 8!, 25}]; lst (* Vladimir Joseph Stephan Orlovsky, Apr 03 2009 *)

Table[5*n*(5*n - 3)/2, {n, 0, 25}] (* or *) LinearRecurrence[{3, -3, 1}, {0, 5, 35}, 25] (* G. C. Greubel, Aug 28 2016 *)

PROG

(PARI) a(n) = 5*n*(5*n-3)/2; \\ Michel Marcus, Aug 28 2016

CROSSREFS

Cf. A000566, A153784, A154786.

Sequence in context: A115707 A117793 A145920 * A090294 A162540 A161199

Adjacent sequences:  A153782 A153783 A153784 * A153786 A153787 A153788

KEYWORD

nonn,easy

AUTHOR

Omar E. Pol, Jan 07 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 June 13 07:45 EDT 2021. Contains 344981 sequences. (Running on oeis4.)