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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A237617 a(n) = n*(n + 1)*(17*n - 14)/6. 2
0, 1, 20, 74, 180, 355, 616, 980, 1464, 2085, 2860, 3806, 4940, 6279, 7840, 9640, 11696, 14025, 16644, 19570, 22820, 26411, 30360, 34684, 39400, 44525, 50076, 56070, 62524, 69455, 76880, 84816, 93280, 102289, 111860, 122010, 132756, 144115, 156104, 168740 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Also 19-gonal (or nonadecagonal) pyramidal numbers.

This sequence is related to A180232 by 2*a(n) = n*A180232(n) - Sum_{i=0..n-1} A180232(i).

REFERENCES

E. Deza and M. M. Deza, Figurate numbers, World Scientific Publishing (2012), page 93 (seventeenth row of the table).

LINKS

Bruno Berselli, Table of n, a(n) for n = 0..1000

Eric Weisstein's World of Mathematics, Pyramidal Number.

Index to sequences related to pyramidal numbers

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

FORMULA

G.f.: x*(1 + 16*x) / (1 - x)^4.

For n>0, a(n) = Sum_{i=0..n-1} (n-i)*(17*i+1); see the generalization in A237616 (Formula field).

EXAMPLE

After 0, the sequence is provided by the row sums of the triangle:

1;

2,  18;

3,  36,  35;

4,  54,  70,  52;

5,  72,  105, 104, 69;

6,  90,  140, 156, 138, 86;

7,  108, 175, 208, 207, 172, 103;

8,  126, 210, 260, 276, 258, 206, 120;

9,  144, 245, 312, 345, 344, 309, 240, 137;

10, 162, 280, 364, 414, 430, 412, 360, 274, 154, etc.,

where (r = row index, c = column index):

T(r,r) = T(c,c) = 17*r-16 and T(r,c) = T(r-1,c)+T(r,r) = (r-c+1)*T(r,r), with r>=c>0.

MATHEMATICA

Table[n (n + 1) (17 n - 14)/6, {n, 0, 40}]

CoefficientList[Series[x (1 + 16 x)/(1 - x)^4, {x, 0, 40}], x] (* Vincenzo Librandi, Feb 12 2014 *)

PROG

(MAGMA) [n*(n+1)*(17*n-14)/6: n in [0..40]];

(MAGMA) I:=[0, 1, 20, 74]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4) : n in [1..50]]; // Vincenzo Librandi, Feb 12 2014

CROSSREFS

Cf. A051871, A180232.

Cf. similar sequences listed in A237616.

Sequence in context: A225923 A238026 A010008 * A000529 A238027 A005565

Adjacent sequences:  A237614 A237615 A237616 * A237618 A237619 A237620

KEYWORD

nonn,easy

AUTHOR

Bruno Berselli, Feb 11 2014

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 June 24 08:38 EDT 2017. Contains 288697 sequences.