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A379006 Ordinal transform of A355582, where A355582 is the largest 5-smooth divisor of n.

%I A379006 #7 Dec 15 2024 11:02:03
%S A379006 1,1,1,1,1,1,2,1,1,1,3,1,4,2,1,1,5,1,6,1,2,3,7,1,1,4,1,2,8,1,9,1,3,5,
%T A379006 2,1,10,6,4,1,11,2,12,3,1,7,13,1,14,1,5,4,15,1,3,2,6,8,16,1,17,9,2,1,
%U A379006 4,3,18,5,7,2,19,1,20,10,1,6,21,4,22,1,1,11,23,2,5,12,8,3,24,1,25,7,9,13,6,1,26,14,3,1,27,5,28,4,2
%N A379006 Ordinal transform of A355582, where A355582 is the largest 5-smooth divisor of n.
%H A379006 Antti Karttunen, <a href="/A379006/b379006.txt">Table of n, a(n) for n = 1..20000</a>
%o A379006 (PARI)
%o A379006 up_to = 20000;
%o A379006 ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om,invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om,invec[i],(1+pt))); outvec; };
%o A379006 is_A051037(n) = (n<7||vecmax(factor(n, 6)[, 1])<7); \\ From A051037
%o A379006 A355582(n) = fordiv(n,d,if(is_A051037(n/d),return(n/d)));
%o A379006 v379006 = ordinal_transform(vector(up_to, n, A355582(n)));
%o A379006 A379006(n) = v379006[n];
%Y A379006 Cf. A355582.
%Y A379006 Cf. A379005 (ordinal transform).
%Y A379006 Cf. also A003602, A126760.
%K A379006 nonn
%O A379006 1,7
%A A379006 _Antti Karttunen_, Dec 15 2024