A181615 Triangle read by rows: T(n,k) = 2^(n-1) mod semiprime(k).

1, 2, 2, 0, 4, 4, 0, 2, 8, 8, 0, 4, 7, 6, 2, 0, 2, 5, 2, 4, 2, 0, 4, 1, 4, 8, 4, 1, 0, 2, 2, 8, 2, 8, 2, 18, 0, 4, 4, 6, 4, 1, 4, 14, 6, 0, 2, 8, 2, 8, 2, 8, 6, 12, 18, 0, 4, 7, 4, 2, 4, 16, 12, 24, 10, 1, 0, 2, 5, 8, 4, 8, 11, 2, 23, 20, 2, 8, 0, 4, 1, 6, 8, 1, 1, 4, 21, 14, 4

Offset: 1

Author

Juri-Stepan Gerasimov, Dec 02 2010

Keywords

• nonn
• tabl

Examples

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

Crossrefs

Cf. A173622, A181670.

Programs

Mathematica

Table[PowerMod[2, n-1, #[[;;n]]], {n, Length[#]}] & [Select[Range[50], PrimeOmega[#] == 2 &]] (* Paolo Xausa, Jun 29 2024 *)

PARI

trg(nn) = {semip = select(n->bigomega(n) == 2, vector(nn, i, i)); for (n = 1, #semip, for (k = 1, n, print1(2^(n-1) % semip[k], ", ");); print(););} \\ Michel Marcus, Sep 11 2013

Extensions

Corrected by T. D. Noe, Dec 02 2010