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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A121281 Triangle T(n,k) read by rows: T(n,0) = A002110(n) and T(n,k) = A002110(n)/prime(k) for 1<=k<=n. 2
1, 2, 1, 6, 3, 2, 30, 15, 10, 6, 210, 105, 70, 42, 30, 2310, 1155, 770, 462, 330, 210, 30030, 15015, 10010, 6006, 4290, 2730, 2310, 510510, 255255, 170170, 102102, 72930, 46410, 39270, 30030, 9699690, 4849845, 3233230, 1939938, 1385670, 881790, 746130, 570570, 510510 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Reinhard Zumkeller, Rows n = 0..120 of triangle, flattened

FORMULA

Sum_{0<=k<=n} T(n,k) = A024528(n).

T(n+1,k) = prime(n+1) * T(n,k) for k=0..n and T(n+1,n+1) = T(n,0). - Reinhard Zumkeller, Nov 20 2015

EXAMPLE

Triangle begins

1;

2, 1;

6, 3, 2;

30, 15, 10, 6;

210, 105, 70, 42, 30;

PROG

(PARI) tabl(nn) = {for (n=0, nn, pr = prod(i=1, n, prime(i)); for (k=0, n, if (k==0, v = pr, v = pr/prime(k)); print1(v, ", "); ); print(); ); } \\ Michel Marcus, Apr 06 2015

(Haskell)

a121281 n k = a121281_tabl !! n !! k

a121281_row n = a121281_tabl !! n

a121281_tabl = [1] : f [1] a000040_list where

   f xs@(x:_) (p:ps) = ys : f ys ps where ys = (map (* p) xs) ++ [x]

-- Reinhard Zumkeller, Nov 20 2015

CROSSREFS

Cf. A000040, A002110, A024528, A070826.

Sequence in context: A097905 A094310 A165908 * A232467 A131449 A289869

Adjacent sequences:  A121278 A121279 A121280 * A121282 A121283 A121284

KEYWORD

nonn,tabl

AUTHOR

Philippe Deléham, Aug 24 2006

EXTENSIONS

Corrected and extended by Michel Marcus, Apr 06 2015

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 February 18 02:20 EST 2018. Contains 299297 sequences. (Running on oeis4.)