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A309476 One of the two successive approximations up to 3^n for the 3-adic integer sqrt(-1/2).

%I A309476 #14 May 11 2020 01:04:58
%S A309476 0,1,7,16,70,232,475,1933,1933,8494,28177,87226,87226,1150108,2744431,
%T A309476 12310369,12310369,55357090,313637416,313637416,1475898883,1475898883,
%U A309476 1475898883,32856958492,221143316146,221143316146,1915720535032,4457586363361,12083183848348,34959976303309
%N A309476 One of the two successive approximations up to 3^n for the 3-adic integer sqrt(-1/2).
%H A309476 Robert Israel, <a href="/A309476/b309476.txt">Table of n, a(n) for n = 0..2093</a>
%e A309476 a(1) = (   1)_3 = 1,
%e A309476 a(2) = (  21)_3 = 7,
%e A309476 a(3) = ( 121)_3 = 16,
%e A309476 a(4) = (2121)_3 = 70.
%p A309476 N:= 30: # for a(0) to a(N)
%p A309476 with(padic):
%p A309476 A:= rootp(x^2+1/2,3,N):
%p A309476 if ratvaluep(A[1],1) = 1 then A:= A[1] else A:= A[2] fi:
%p A309476 seq(ratvaluep(A,i),i=0..N); # _Robert Israel_, May 11 2020
%o A309476 (PARI) {a(n) = truncate(sqrt(-1/2+O(3^n)))}
%Y A309476 Cf. A268924, A309474, A309477.
%K A309476 nonn
%O A309476 0,3
%A A309476 _Seiichi Manyama_, Aug 04 2019