A319698 Filter sequence combining A003557(n) [n divided by largest squarefree divisor of n] with A319697(n) [sum of even squarefree divisors of n].

1, 2, 1, 3, 1, 4, 1, 5, 6, 7, 1, 8, 1, 9, 1, 10, 1, 11, 1, 12, 1, 13, 1, 14, 15, 16, 17, 18, 1, 19, 1, 20, 1, 21, 1, 22, 1, 23, 1, 24, 1, 25, 1, 26, 6, 19, 1, 27, 28, 29, 1, 30, 1, 31, 1, 32, 1, 33, 1, 34, 1, 25, 6, 35, 1, 36, 1, 37, 1, 36, 1, 38, 1, 39, 15, 40, 1, 41, 1, 42, 43, 44, 1, 45, 1, 46, 1, 47, 1, 48, 1, 34, 1, 36, 1, 49, 1, 50, 6, 51, 1, 52, 1, 53, 1

Offset: 1

Author

Antti Karttunen, Oct 31 2018

Keywords

• nonn

Comments

Restricted growth sequence transform of ordered pair [A003557(n), A319697(n)].

Links

• Antti Karttunen, Table of n, a(n) for n = 1..65537

Crossrefs

Cf. A003557, A319697.

Cf also A291750, A291751.

Programs

PARI

up_to = 65537;
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; };
A003557(n) = { my(f=factor(n)); for (i=1, #f~, f[i, 2] = f[i, 2]-1); factorback(f); }; \\ From A003557
A319697(n) = sumdiv(n, d, (!(d%2))*issquarefree(d)*d);
v319698 = rgs_transform(vector(up_to,n,[A003557(n),A319697(n)]));
A319698(n) = v319698[n];