A077661 Triangle read by rows in which the n-th row contains n smallest numbers not coprime to n; except first row = {1}.

1, 2, 4, 3, 6, 9, 2, 4, 6, 8, 5, 10, 15, 20, 25, 2, 3, 4, 6, 8, 9, 7, 14, 21, 28, 35, 42, 49, 2, 4, 6, 8, 10, 12, 14, 16, 3, 6, 9, 12, 15, 18, 21, 24, 27, 2, 4, 5, 6, 8, 10, 12, 14, 15, 16, 11, 22, 33, 44, 55, 66, 77, 88, 99, 110, 121, 2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18

Offset

1,2

Links

Alois P. Heinz, Rows n = 1..200, flattened

Example

Triangle begins as:
  1;
  2,  4;
  3,  6,  9;
  2,  4,  6,  8;
  5, 10, 15, 20, 25;
  2,  3,  4,  6,  8,  9;
  7, 14, 21, 28, 35, 42, 49;
  ...

Mathematica

Join[{1}, Table[Take[Select[Range[n^2], GCD[#, n]!=1 &], n], {n, 2, 13}]]//Flatten (* Stefano Spezia, Jan 10 2025 *)

Crossrefs

Cf. A077662, A077663.

Sequence in context: A175334 A128556 A212485 * A077583 A153125 A391245

Adjacent sequences: A077658 A077659 A077660 * A077662 A077663 A077664

Keyword

nonn,look,tabl

Author

Amarnath Murthy, Nov 14 2002

Extensions

More terms from Sascha Kurz, Jan 27 2003

Status

approved