OFFSET
1,2
COMMENTS
Similar to A037197 but using tau#(n), number of the least divisors of n whose LCM is equal to n, as defined in A222084, and sigma#(n), sum of the least divisors of n whose LCM is equal to n, as defined in A222085: tau#(n)=tau#(sigma#(n)).
If we add also the restriction tau(n)=tau(sigma(n)) we have: 2, 52, 1525, 83667, 116162,…
LINKS
Paolo P. Lava, Table of n, a(n) for n = 1..1000
EXAMPLE
n=20; tau#(20)=4, sigma#(20)=12 and tau#(sigma#(20))=tau#(12)=4.
MAPLE
with(numtheory);
A222087:=proc(q)
local a, b, c, j, n, t, v;
print(1);
for n from 2 to q do
a:=ifactors(n)[2]; b:=nops(a); c:=0; v:=0;
for j from 1 to b do if a[j][1]^a[j][2]>c then c:=a[j][1]^a[j][2]; fi; od;
a:=op(sort([op(divisors(n))])); b:=nops(divisors(n));
for j from 1 to b do v:=v+a[j]; if a[j]=c then break; fi; od; t:=j;
a:=ifactors(v)[2]; b:=nops(a); c:=0;
for j from 1 to b do if a[j][1]^a[j][2]>c then c:=a[j][1]^a[j][2]; fi; od;
a:=op(sort([op(divisors(v))])); b:=nops(divisors(v));
for j from 1 to b do if a[j]=c then break; fi; od; if t=j then print(n);
fi; od; end:
A222087(10000000000);
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Feb 13 2013
STATUS
approved