A357529 Triangular numbers k such that 2*k cannot be expressed as a sum of two distinct triangular numbers.

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

Author

Stefano Spezia, Oct 02 2022

Keywords

• nonn
• easy

Comments

Subset of even terms of A357505, divided by 2. - Michel Marcus, 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.

Programs

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 *)