A323405 - OEIS

%I #11 Jan 13 2019 19:30:11

%S 1,2,3,4,3,5,3,6,7,8,3,9,3,10,11,12,3,13,3,14,15,16,3,17,18,19,20,21,

%T 3,22,3,23,24,25,26,27,3,28,26,29,3,30,3,31,32,33,3,34,35,36,37,38,3,

%U 39,40,41,42,43,3,44,3,45,46,47,48,49,3,50,51,52,3,53,3,54,55,56,57,58,3,59,60,61,3,62,63,64,65,66,3,67,68,69,57,70,71,72,3,73,74,75,3

%N Lexicographically earliest sequence such that for all i, j, a(i) = a(j) => f(i) = f(j) where f(n) = [A003557(n), A023900(n), A063994(n)] for all other numbers, except f(n) = 0 for odd primes.

%C For all i, j:

%C   A305801(i) = A305801(j) => a(i) = a(j),

%C   a(i) = a(j) => A323371(i) = A323371(j),

%C   a(i) = a(j) => A247074(i) = A247074(j).

%H Antti Karttunen, <a href="/A323405/b323405.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 A003557(n) = { my(f=factor(n)); for (i=1, #f~, f[i, 2] = max(0,f[i, 2]-1)); factorback(f); };

%o A023900(n) = sumdivmult(n, d, d*moebius(d)); \\ From A023900

%o A063994(n) = { my(f=factor(n)[, 1]); prod(i=1, #f, gcd(f[i]-1, n-1)); }; \\ From A063994

%o Aux323405(n) = if((n>2)&&isprime(n),0,[A003557(n), A023900(n), A063994(n)]);

%o v323405 = rgs_transform(vector(up_to, n, Aux323405(n)));

%o A323405(n) = v323405[n];

%Y Cf. A000010, A003557, A023900, A063994, A247074, A305801, A323371, A323404.

%Y Differs from A323370 for the first time at n=78, where a(78) = 58, while A323370(78) = 52.

%Y Cf. also A323374.

%K nonn

%O 1,2

%A _Antti Karttunen_, Jan 13 2019