cp's OEIS Frontend

A319339 Filter sequence combining A081373(n) with A246277(n).

%I A319339 #6 Sep 24 2018 17:46:33
%S A319339 1,2,3,4,3,5,3,6,4,7,3,8,3,9,10,11,3,12,3,13,14,15,3,16,17,18,6,19,3,
%T A319339 20,3,21,22,23,10,24,3,25,15,26,3,27,3,28,29,30,3,31,4,32,33,34,3,35,
%U A319339 14,36,37,38,3,39,3,40,13,41,42,43,3,44,45,46,3,47,3,48,49,50,51,52,3,53,54,55,3,56,57,58,59,60,3,61,14,62,63,64,18,65,3,66,19
%N A319339 Filter sequence combining A081373(n) with A246277(n).
%C A319339 Restricted growth sequence transform of ordered pair [A081373(n), A246277(n)].
%H A319339 Antti Karttunen, <a href="/A319339/b319339.txt">Table of n, a(n) for n = 1..65537</a>
%o A319339 (PARI)
%o A319339 up_to = 65537;
%o A319339 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 A319339 rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
%o A319339 v081373 = ordinal_transform(vector(up_to,n,eulerphi(n)));
%o A319339 A081373(n) = v081373[n];
%o A319339 A246277(n) = if(1==n, 0, my(f = factor(n), k = primepi(f[1,1])-1); for (i=1, #f~, f[i,1] = prime(primepi(f[i,1])-k)); factorback(f)/2);
%o A319339 v319339 = rgs_transform(vector(up_to,n,[A081373(n),A246277(n)]));
%o A319339 A319339(n) = v319339[n];
%Y A319339 Cf. A081373, A246277, A300247, A305801, A305897, A318500.
%K A319339 nonn
%O A319339 1,2
%A A319339 _Antti Karttunen_, Sep 24 2018