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a(n) = (A266203(n)-1)/2 if n>0, and a(0) = 0.
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%I #19 Jan 11 2020 15:57:47

%S 0,0,1,2,10,30,190,1022

%N a(n) = (A266203(n)-1)/2 if n>0, and a(0) = 0.

%C The maximum values of k where g_k(n) is the maximal value.

%C g_k(n) is the weak Goodstein function defined in A266202.

%C Next term: 3*2^402653210-1.

%e g_1(4) = b_2(4)-1 = b_2(2^2)-1 = 3^2-1 = 8;

%e g_2(4) = b_3(2*3+2)-1 = 2*4 + 2-1 = 9;

%e g_3(4) = b_4(2*4 + 1 ) -1 = 2*5 + 1-1 = 10;

%e g_4(4) = b_5(2*5) -1= 2*6 - 1 = 11;

%e g_5(4) = b_6(6+5)-1 = 7+5-1 = 11;

%e g_6(4) = b_7(7+4)-1 = 8+4-1 = 11;

%e g_7(4) = b_8(8+3)-1 = 9+3-1 = 11;

%e g_8(4) = b_9(9+2)-1 = 10+2-1 = 11;

%e g_9(4) = b_10(10+1)-1 = 11+1-1 = 11;

%e g_10(4) = b_11(11)-1 = 12-1 = 11;

%e g_11(4) = b_12(11)-1 = 11-1 = 10;

%e g_12(4) = b_13(10)-1 = 10-1 = 9;

%e g_13(4) = b_14(9)-1 = 9-1 = 8;

%e …

%e g_21(4) = 0;

%e So a(4) = 10.

%Y Cf. A266203, A268687, A268689.

%K nonn

%O 0,4

%A _Natan Arie Consigli_, Apr 02 2016