The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A117265 Triangle T, read by rows, where matrix power T^-2 has -2^(n+1) in the secondary diagonal: [T^-2](n+1,n) = -2^(n+1), with all 1's in the main diagonal and zeros elsewhere. 8
 1, 1, 1, 3, 2, 1, 20, 12, 4, 1, 280, 160, 48, 8, 1, 8064, 4480, 1280, 192, 16, 1, 473088, 258048, 71680, 10240, 768, 32, 1, 56229888, 30277632, 8257536, 1146880, 81920, 3072, 64, 1, 13495173120, 7197425664, 1937768448, 264241152, 18350080, 655360 (list; table; graph; refs; listen; history; text; internal format)
 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=-2, q=2, r=1. LINKS Table of n, a(n) for n=0..41. FORMULA T(n,k) = A086229(n-k)*2^((n-k)*k). T(n,k) = 2^(n*(n-1)/2-k*(k-1)/2)/(n-k)!*prod_{j=0..n-k-1}(2*j+1) for n>k>=0, with T(n,n) = 1. EXAMPLE Triangle T begins: 1; 1,1; 3,2,1; 20,12,4,1; 280,160,48,8,1; 8064,4480,1280,192,16,1; 473088,258048,71680,10240,768,32,1; 56229888,30277632,8257536,1146880,81920,3072,64,1; 13495173120,7197425664,1937768448,264241152,18350080,655360,12288,128,1; Matrix inverse square T^-2 has -2^(n+1) in the 2nd diagonal: 1; -2,1; 0,-4,1; 0,0,-8,1; 0,0,0,-16,1; 0,0,0,0,-32,1; 0,0,0,0,0,-64,1; ... PROG (PARI) {T(n, k)=local(m=1, p=-2, q=2, r=1); prod(j=0, n-k-1, m*r-p*j)/(n-k)!*q^((n-k)*(n+k-1)/2)} CROSSREFS Cf. A086229 (column 0), A117266 (row sums); variants: A117250 (p=q=2), A117252 (p=q=3), A117254 (p=q=4), A117256 (p=q=5), A117258 (p=2, q=4), A117260 (p=-1, q=2), A117262 (p=-1, q=3). Sequence in context: A117269 A291080 A107862 * A107727 A346743 A087041 Adjacent sequences: A117262 A117263 A117264 * A117266 A117267 A117268 KEYWORD nonn,tabl AUTHOR Paul D. Hanna, Mar 14 2006 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 29 13:06 EST 2023. Contains 367445 sequences. (Running on oeis4.)