A173662 Triangle read by rows: T(n,k) = semiprime(n) mod semiprime(k), 1 <= k <= n.

0, 2, 0, 1, 3, 0, 2, 4, 1, 0, 2, 2, 5, 4, 0, 3, 3, 6, 5, 1, 0, 1, 3, 3, 1, 7, 6, 0, 2, 4, 4, 2, 8, 7, 1, 0, 1, 1, 7, 5, 11, 10, 4, 3, 0, 2, 2, 8, 6, 12, 11, 5, 4, 1, 0, 1, 3, 6, 3, 5, 3, 12, 11, 8, 7, 0, 2, 4, 7, 4

Offset

1,2

Comments

Row sums are 0, 2, 4, 7, 13, 18, 28, ...

Links

Table of n, a(n) for n=1..70.

Example

Triangle begins:
  0,
  2,0;
  1,3,0;
  2,4,1,0;
  2,2,5,4,0;
  3,3,6,5,1,0;
  1,3,3,1,7,6,0;
  2,4,4,2,8,7,1,0;

Mathematica

SemiprimeQ[n_Integer] := If[Abs[n]<2, False, (2==Plus@@Transpose[FactorInteger[Abs[n]]][[2]])]; sp = Select[Range[100], SemiprimeQ]; Flatten[Table[Mod[sp[[n]], sp[[Range[n]]]], {n, Length[sp]}]]

Crossrefs

Cf. A001358, A173655.

Sequence in context: A128097 A328096 A353778 * A263406 A257230 A357136

Adjacent sequences: A173659 A173660 A173661 * A173663 A173664 A173665

Keyword

nonn,tabl,easy

Author

Juri-Stepan Gerasimov, Nov 28 2010

Extensions

46th term corrected by D. S. McNeil, Nov 24 2010

Status

approved