A117252 Triangle T, read by rows, where matrix power T^3 has powers of 3 in the secondary diagonal: [T^3](n+1,n) = 3^(n+1), with all 1's in the main diagonal and zeros elsewhere.

1, 1, 1, -3, 3, 1, 45, -27, 9, 1, -2430, 1215, -243, 27, 1, 433026, -196830, 32805, -2187, 81, 1, -245525742, 105225318, -15943230, 885735, -19683, 243, 1, 434685788658, -178988265918, 25569752274, -1291401630, 23914845, -177147, 729, 1

Offset

0,4

Comments

More generally, if a lower triangular matrix T to the power p is given by: [T^p](n,k) = C(r,n-k)*p^(n-k)*q^(n*(n-1)/2-k*(k-1)/2) then, for all m, [T^m](n,k) = [prod_{j=0..n-k-1}(m*r-p*j)]/(n-k)!*q^(n*(n-1)/2-k*(k-1)/2) for n>k>=0, with T(n,n) = 1. This triangle results when m=1, p=3, q=3, r=1.

Links

Table of n, a(n) for n=0..35.

Formula

T(n,k) = A117253(n-k)*3^((n-k)*k). T(n,k) = [prod_{j=0..n-k-1}(1-3*j)]/(n-k)!*3^(n*(n-1)/2-k*(k-1)/2) for n>k>=0, with T(n,n) = 1.

Example

Triangle T begins:
1;
1,1;
-3,3,1;
45,-27,9,1;
-2430,1215,-243,27,1;
433026,-196830,32805,-2187,81,1;
-245525742,105225318,-15943230,885735,-19683,243,1;
434685788658,-178988265918,25569752274,-1291401630,23914845,-177147,729,1;
Matrix cube T^3 has powers of 3 in the 2nd diagonal:
1;
3,1;
0,9,1;
0,0,27,1;
0,0,0,81,1;
0,0,0,0,243,1;
0,0,0,0,0,729,1; ...

Prog

(PARI) {T(n, k)=local(m=1, p=3, q=3, r=1); prod(j=0, n-k-1, m*r-p*j)/(n-k)!*q^((n-k)*(n+k-1)/2)}

Crossrefs

Cf. A117253 (column 0); variants: A117250 (p=q=2), A117254 (p=q=4), A117256 (p=q=5), A117258 (p=2, q=4), A117260 (p=-1, q=2), A117262 (p=-1, q=3), A117265 (p=-2, q=2).

Sequence in context: A065431 A271082 A053375 * A332498 A181407 A114187

Adjacent sequences: A117249 A117250 A117251 * A117253 A117254 A117255

Keyword

sign,tabl

Author

Paul D. Hanna, Mar 14 2006

Status

approved