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A175620 Triangle read by rows: T(n,k) = 2^(prime(n) - k - 1) mod n, 1 <= k <= n.

%I A175620 #23 Apr 13 2024 01:50:16
%S A175620 0,0,1,2,1,2,0,0,0,0,2,1,3,4,2,2,4,2,4,2,4,1,4,2,1,4,2,1,0,0,0,0,0,0,
%T A175620 0,0,8,4,2,1,5,7,8,4,2,8,4,2,6,8,4,2,6,8,4,6,3,7,9,10,5,8,4,2,1,6,8,4,
%U A175620 8,4,8,4,8,4,8,4,8,4,8,4,2,1,7,10,5,9,11,12,6,3,8
%N A175620 Triangle read by rows: T(n,k) = 2^(prime(n) - k - 1) mod n, 1 <= k <= n.
%H A175620 Harvey P. Dale, <a href="/A175620/b175620.txt">Table of n, a(n) for n = 1..10000</a>
%e A175620 Triangle begins:
%e A175620   0;
%e A175620   0, 1;
%e A175620   2, 1, 2;
%e A175620   0, 0, 0, 0;
%e A175620   2, 1, 3, 4, 2;
%e A175620   2, 4, 2, 4, 2, 4;
%p A175620 A175620 := proc(n,k) modp(2^(ithprime(n)-k-1) ,n) ; end proc: # _R. J. Mathar_, Dec 14 2010
%t A175620 Flatten[Table[PowerMod[2,Prime[n]-k-1,n],{n,20},{k,n}]] (* _Harvey P. Dale_, Dec 10 2012 *)
%o A175620 (Magma)
%o A175620 [Modexp(2,NthPrime(n)-k-1,n): k in [1..n], n in [1..15]]; // _G. C. Greubel_, Apr 12 2024
%o A175620 (SageMath)
%o A175620 flatten([[pow(2,nth_prime(n)-k-1,n) for k in range(1,n+1)] for n in range(1,16)]) # _G. C. Greubel_, Apr 12 2024
%Y A175620 Cf. A000079, A173655, A177226.
%K A175620 nonn,tabl
%O A175620 1,4
%A A175620 _Juri-Stepan Gerasimov_, Dec 12 2010