A352243 Positive integers of the form (x-y)*(x^3-y^3).

7, 19, 37, 52, 61, 91, 112, 127, 169, 189, 196, 217, 271, 304, 331, 351, 397, 436, 469, 496, 547, 567, 592, 631, 721, 772, 817, 832, 837, 919, 976, 1027, 1075, 1141, 1161, 1204, 1261, 1264, 1387, 1456, 1519, 1539, 1657, 1675, 1732, 1792, 1801, 1951, 1971, 2032, 2052

Offset: 1

Author

Michel Marcus, Mar 09 2022

Keywords

• nonn

Comments

Integers that are in the A352242 triangle.

Examples

			7, 19, 37, 52 and 61 are respectively A352242(1,1), A352242(2,2), A352242(3,3), A352242(2,1) and A352242(4,4).
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A352242, A352244.

Programs

Maple

N:= 10^4: # for terms <= N
S:= {}:
for y from 1 while 3*y^2 + 3*y + 1 <= N do
  for x from y+1 do
    v:= (x-y)*(x^3-y^3);
    if v > N then break fi;
    S:= S union {v};
od; od:
sort(convert(S,list)); # Robert Israel, May 16 2024

PARI

row(n) = vector(n-1, k, (n-k)*(n^3-k^3));
lista(nn) = {my(list = List(), n=2); while (3*n*(n-1)+1 <= nn, my(rown = row(n)); for (k=1, #rown, if (rown[k] <= nn, listput(list, rown[k]))); n++;); Set(Vec(list));}