OFFSET
1,2
FORMULA
From Tristan Cam, Oct 02 2024: (Start)
a(1) = 1, a(n) = a(n-1)*(1+3*2^(n-2)) (conjectured).
a(n) = Product_{k=1..n-1} 1+3*2^(k-1) = QPochhammer[-3, 2, n-1]. (conjectured). (End)
MAPLE
A155102 := proc(n, k) if n = k then 1 ; elif n =2*k then -k-1 ; else 0; end if; end proc:
for r from 1 to amx do
for c from 1 to r-1 do a[c, r] := 0 ; end do:
a[r, r] := 1/A155102(r, r) ;
if c = 3 and a[r, c] <> 0 then print( a[r, c]) ; end if;
end do:
end do:
return ;
end proc:
A155103(290) ; # R. J. Mathar, Dec 07 2010
PROG
(PARI) \\ after R. J. Mathar
T(n, k)=if(n==k, 1, if(n==2*k, -(k+1))); \\ from A155102
\\ First term = 1 omitted
a155103(upto) = my(m=3*2^upto, a=matid(m)); for(r=1, m, forstep(c=r-1, 1, -1, a[r, c]=-sum(cp=c, r-1, a[cp, c]*T(r, cp)); if(c==3 && a[r, c]!=0, print1(a[r, c], ", "))));
a155103(8) \\ Hugo Pfoertner, Oct 03 2024
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Mats Granvik, Jan 20 2009
EXTENSIONS
Two more terms from R. J. Mathar, Dec 07 2010
a(8)-a(12) from Hugo Pfoertner, Oct 02 2024
STATUS
approved