OFFSET
1,2
COMMENTS
LINKS
EXAMPLE
Triangle begins:
1;
5, 4;
7, 6, 2;
17, 16, 12, 10;
20, 19, 15, 13, 3;
...
MATHEMATICA
nmax = 9;
differenceQ[seq_, x_] := Module[{r = False}, Do[If[x==seq[[k]] - seq[[j]], r = True; Break[]], {j, 1, Length[seq]}, {k, 1, Length[seq]}]; r];
seq[1] = {1, 2};
seq[i_] := seq[i] = Module[{j, k}, k = Max[seq[i-1]]; j = First[Select[ Range[k], !differenceQ[seq[i-1], #]&, 1]]; Union[seq[i-1], {2k+2, 2k+2+j}]];
A024431 = seq[nmax];
Table[T[n, k], {n, 1, nmax}, {k, 1, n}] // Flatten (* Jean-François Alcover, Sep 20 2021 *)
PROG
(Haskell)
import Data.List (inits)
a115409 n k = a115409_tabl !! (n-1) !! (k-1)
a115409_row n = a115409_tabl !! (n-1)
a115409_tabl = map f $ drop 2 $ inits a024431_list where
f xs = reverse $ map (z -) zs where (z:zs) = reverse xs
a115409_list = concat a115409_tabl
-- Reinhard Zumkeller, Sep 16 2014
CROSSREFS
AUTHOR
Reinhard Zumkeller, Jan 22 2006
STATUS
approved