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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A248668 Sum of the numbers in the n-th row of the array at A248664. 7
1, 4, 26, 260, 3610, 64472, 1409006, 36432076, 1087911890, 36844580000, 1395429571222, 58439837713556, 2681526361893626, 133783187672365480, 7210345924097089790, 417482356526745344732, 25844171201928905477026, 1703359919973405018460976 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The polynomial p(n,x) is defined as the numerator when the sum 1 + 1/(n*x + 1) + 1/((n*x + 1)(n*x + 2)) + ... + 1/((n*x + 1)(n*x + 2)...(n*x + n - 1)) is written as a fraction with denominator (n*x + 1)(n*x + 2)...(n*x + n - 1). For more, see A248664.

LINKS

Table of n, a(n) for n=1..18.

FORMULA

a(n) = p(n,1), where p(n,x) is defined at A248664.

a(n) = Sum_{k = 0..n-1} k!*binomial(2*n-1,k). - Peter Bala, Nov 14 2017

a(n) = A294039(n) - Pochhammer(n, n)*A000522(n). - Peter Luschny, Nov 14 2017

EXAMPLE

The first six polynomials:

p(1,x) = 1

p(2,x) = 2 (x + 1)

p(3,x) = 9x^2 + 12 x +  5

p(4,x) = 4 (16 x^3 + 28 x^2 + 17 x + 4)

p(5,x) = 5 (125 x^4 + 275 x^3 + 225 x^2 + 84 x + 13)

p(6,x) = 2 (3888 x^5 + 10368 x^4 + 10800 x^3 + 5562 x^2 + 1455 x + 163), so that

a(1) = p(1,1) = 1, a(2) = p(2,1) = 4, a(3) = p(3,1) = 26.

MAPLE

with (combinat):

seq(add( k!*binomial(2*n-1, k), k = 0..n-1 ), n = 0..20);

# Peter Bala, Nov 14 2017

MATHEMATICA

t[x_, n_, k_] := t[x, n, k] = Product[n*x + n - i, {i, 1, k}];

p[x_, n_] := Sum[t[x, n, k], {k, 0, n - 1}];

TableForm[Table[Factor[p[x, n]], {n, 1, 6}]]

c[n_] := c[n] = CoefficientList[p[x, n], x];

TableForm[Table[c[n], {n, 1, 10}]] (* A248664 array *)

Table[Apply[Plus, c[n]], {n, 1, 60}] (* A248668 *)

PROG

(PARI) a(n) = sum(k = 0, n-1, k!*binomial(2*n-1, k)); \\ Michel Marcus, Nov 15 2017

CROSSREFS

Cf. A000522, A248664, A248665, A248666, A248669, A294039.

Sequence in context: A098620 A215266 A002465 * A079473 A145164 A113078

Adjacent sequences:  A248665 A248666 A248667 * A248669 A248670 A248671

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Oct 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 18 10:08 EST 2019. Contains 329261 sequences. (Running on oeis4.)