A318881 - OEIS

%I #6 Sep 17 2018 15:45:18

%S 1,1,2,2,3,2,4,3,4,3,4,3,5,4,6,6,7,4,5,6,5,4,4,6,5,5,5,5,5,6,8,7,5,7,

%T 9,5,10,5,9,7,9,5,8,5,9,4,4,7,8,5,11,9,5,5,9,9,10,5,4,7,12,8,10,11,13,

%U 5,8,11,5,9,8,9,14,10,9,10,12,9,8,11,9,9,4,9,15,8,9,9,9,9,14,5,12,4,14,11,16,8,12,9,10,11,8,13,13

%N Restricted growth sequence transform of A277906, the least number with same prime signature as phi(n).

%H Antti Karttunen, <a href="/A318881/b318881.txt">Table of n, a(n) for n = 1..65537</a>

%o (PARI)

%o up_to = 65537;

%o 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 A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ From A046523

%o A277906(n) = A046523(eulerphi(n));

%o v318881 = rgs_transform(vector(up_to,n,A277906(n)));

%o A318881(n) = v318881[n];

%Y Cf. A000010, A046523, A277906, A319342, A319343, A319344, A319345.

%K nonn

%O 1,3

%A _Antti Karttunen_, Sep 17 2018