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!)
A249831 A(n,n) = 1, A(n,k) = A(n,k+1)*k / gcd(A(n,k+1),k)^2 if n>k, A(n,k) = A(n,k-1)*k / gcd(A(n,k-1),k)^2 if n<k; square array A(n,k), n>=1, k>=1, read by antidiagonals. 3
1, 2, 1, 6, 1, 2, 6, 3, 2, 6, 30, 12, 1, 6, 6, 5, 60, 4, 3, 6, 30, 35, 10, 20, 1, 12, 30, 5, 280, 70, 30, 5, 4, 60, 5, 35, 2520, 140, 210, 30, 1, 20, 10, 35, 70, 252, 1260, 420, 210, 6, 5, 30, 70, 70, 70, 2772, 126, 420, 420, 42, 1, 30, 210, 35, 70, 7 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Alois P. Heinz, Antidiagonals n = 1..141, flattened

EXAMPLE

Square array A(n,k) begins:

:   1,  2,  6,   6,  30,  5,  35, 280, 2520,  252, ...

:   1,  1,  3,  12,  60, 10,  70, 140, 1260,  126, ...

:   2,  2,  1,   4,  20, 30, 210, 420,  420,   42, ...

:   6,  6,  3,   1,   5, 30, 210, 420,  420,   42, ...

:   6,  6, 12,   4,   1,  6,  42,  84,   84,  210, ...

:  30, 30, 60,  20,   5,  1,   7,  56,  504, 1260, ...

:   5,  5, 10,  30,  30,  6,   1,   8,   72,  180, ...

:  35, 35, 70, 210, 210, 42,   7,   1,    9,   90, ...

:  70, 70, 35, 105, 420, 84,  56,   8,    1,   10, ...

:  70, 70, 35, 105, 420, 84, 504,  72,    9,    1, ...

MAPLE

A:= proc(n, k) option remember; `if`(k=n, 1,

      (r-> r*k/igcd(r, k)^2)(A(n, k+`if`(n>k, 1, -1))))

    end:

seq(seq(A(n, 1+d-n), n=1..d), d=1..14);

MATHEMATICA

A[n_, k_] := A[n, k] = If[k == n, 1, Function[{r}, r*k/GCD[r, k]^2][A[n, k+If[n>k, 1, -1]]]]; Table[Table[A[n, 1+d-n], {n, 1, d}], {d, 1, 14}] // Flatten (* Jean-François Alcover, Dec 02 2014, translated from Maple *)

CROSSREFS

Column k=1 gives A055204(n-1) for n>1.

Row n=1 gives A008339(k+1).

Main diagonal gives: A000012.

Sequence in context: A085099 A193807 A225766 * A304527 A321725 A154744

Adjacent sequences:  A249828 A249829 A249830 * A249832 A249833 A249834

KEYWORD

nonn,tabl,look

AUTHOR

Alois P. Heinz, Nov 06 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 January 28 00:31 EST 2020. Contains 331312 sequences. (Running on oeis4.)