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A236847 Greatest inverse of A234742: a(n) = maximal k such that when it is remultiplied "upwards", from GF(2)[X] to N, the result is n, and 0 if no such k exists.

%I A236847 #12 Feb 28 2014 06:08:46
%S A236847 0,1,2,3,4,0,6,7,8,5,0,11,12,13,14,0,16,0,10,19,0,9,22,0,24,25,26,15,
%T A236847 28,0,0,31,32,29,0,0,20,37,38,23,0,41,18,0,44,0,0,47,48,21,50,0,52,0,
%U A236847 30,55,56,53,0,59,0,61,62,27,64,0,58,67,0,0,0,0,40,73,74,43,76,49,46,0,0,17,82,0,36,0,0,87,88,0,0,91
%N A236847 Greatest inverse of A234742: a(n) = maximal k such that when it is remultiplied "upwards", from GF(2)[X] to N, the result is n, and 0 if no such k exists.
%C A236847 Apart from zero, each term occurs at most once. 35 is the smallest positive integer not present in this sequence.
%H A236847 Antti Karttunen, <a href="/A236847/b236847.txt">Table of n, a(n) for n = 0..8192</a>
%F A236847 a(n) = maximal k such that A234742(k) = n, and 0 if no such k exists.
%F A236847 For all n, a(n) <= n.
%o A236847 (Scheme) (define (A236847 n) (let loop ((i n)) (cond ((zero? i) i) ((= (A234742 i) n) i) (else (loop (- i 1))))))
%Y A236847 Differs from A236846 for the first time at n=91, where a(91) = 91, while A236846(91) = 35.
%Y A236847 A236844 gives the positions of zeros.
%Y A236847 Cf. A234742.
%Y A236847 Cf. also A236836, A236837.
%K A236847 nonn
%O A236847 0,3
%A A236847 _Antti Karttunen_, Jan 31 2014