A180430 - OEIS

A180430

Triangle T(n,k) defined by the recurrence in the formula.

1, 1, 2, 1, 0, 2, 1, 2, -2, 2, 1, 0, 2, -2, 2, 1, 2, 0, 0, -2, 2, 1, 0, 0, 2, 0, -2, 2, 1, 2, 0, 0, 0, 0, -2, 2, 1, 0, 2, -2, 2, 0, 0, -2, 2, 1, 2, -2, 2, 0, 0, 0, 0, -2, 2, 1, 0, 2, 0, -2, 2, 0, 0, 0, -2, 2, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, -2, 2, 1, 0, 0, 0, 2, -2, 2, 0, 0, 0, 0, -2, 2, 1, 2, 0, 0, 0, 0, 0, 0

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Table of n, a(n) for n=1..99.

FORMULA

T(n,1)=1. T(n,2) = 2-T(n-1,2). T(n,k) = Sum_{i=1..k-2} T(n-i,k-1) - Sum{i=1..k-1} T(n-i,k) for k > 2.

EXAMPLE

Table starts:

1, 2;

1, 0, 2;

1, 2, -2, 2;

1, 0, 2, -2, 2;

1, 2, 0, 0, -2, 2;

1, 0, 0, 2, 0, -2, 2;

1, 2, 0, 0, 0, 0, -2, 2;

1, 0, 2, -2, 2, 0, 0, -2, 2;

1, 2, -2, 2, 0, 0, 0, 0, -2, 2;

MAPLE

A180430 := proc(n, k) option remember; if k>n then 0; elif k = 1 then 1; elif k = 2 then 2-procname(n-1, k) ; else add( procname(n-i, k-1), i=1..k-2) - add(procname(n-i, k), i=1..k-1) ; end if; end proc: # R. J. Mathar, Jul 13 2011

PROG

(Excel) Using European dot comma style:

=if(column()=1; 1; if(row()>=column(); sum(indirect(address(row()-column()+2; column()-1; 4)&":"&address(row()-1; column()-1; 4); 4))-sum(indirect(address(row()-column()+1; column(); 4)&":"&address(row()-1; column(); 4); 4)); 0))

CROSSREFS

Cf. A176702.

Sequence in context: A333948 A287360 A035443 * A246369 A036261 A140575

Adjacent sequences: A180427 A180428 A180429 * A180431 A180432 A180433

KEYWORD

sign,tabl

AUTHOR

Mats Granvik, Sep 04 2010

STATUS

approved