%I #21 Jun 29 2024 16:03:07

%S 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,

%T 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,

%U 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

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

%e Triangle begins:

%e 1;

%e 2, 2;

%e 0, 4, 4;

%e 0, 2, 8, 8;

%e 0, 4, 7, 6, 2;

%e ...

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

%o (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

%Y Cf. A173622, A181670.

%K nonn,tabl

%O 1,2

%A _Juri-Stepan Gerasimov_, Dec 02 2010

%E Corrected by _T. D. Noe_, Dec 02 2010