login
A357529
Triangular numbers k such that 2*k cannot be expressed as a sum of two distinct triangular numbers.
2
0, 1, 6, 10, 15, 45, 55, 66, 91, 120, 136, 231, 276, 300, 406, 435, 496, 561, 595, 630, 741, 780, 820, 861, 1081, 1225, 1326, 1431, 1830, 2016, 2080, 2145, 2211, 2415, 2485, 2701, 2850, 3240, 3321, 3486, 3655, 3916, 4005, 4465, 4560, 4950, 5050, 5356, 5460, 5565
OFFSET
1,3
COMMENTS
Subset of even terms of A357505, divided by 2. - Michel Marcus, Nov 05 2022
MATHEMATICA
TriangularQ[n_]:=IntegerQ[(Sqrt[1+8n]-1)/2]; A000217[n_]:=n(n+1)/2; a={}; For[k=0, k<=105, k++, ok=1; For[h=0, h<2k, h++, If[TriangularQ[2*A000217[k] - A000217[h]] && k!=h, ok=0]]; If[ok==1, AppendTo[a, k(k+1)/2]]]; a (* Stefano Spezia, Nov 05 2022 *)
CROSSREFS
Cf. A000217 (supersequence), A002378.
Half of the complement of A357504 in A020756.
Half of the complement of A020757 in A357505.
Subsequence of A008851.
Sequence in context: A238047 A272398 A020159 * A048017 A332392 A048078
KEYWORD
nonn,easy
AUTHOR
Stefano Spezia, Oct 02 2022
STATUS
approved