OFFSET
1,2
COMMENTS
Conjecture: this is a permutation of the natural numbers.
EXAMPLE
a(1)=1 and n=1 is odd -> a(2)=2 because is the smallest number not yet in the sequence such that a(1) || a(2) = 12 is abundant.
Now n=2 is even -> a(3)=3 because is the smallest number not yet in the sequence such that a(2) || a(3) = 23 is deficient. And so on.
MAPLE
with(numtheory): P:=proc(q) local a, b, k, n; a:=[1, 2, 3, 0]; for n from 5 to q do
for k from 4 do if numboccur(k, a)=0 then b:=a[nops(a)]*10^length(k)+k;
if (n mod 2=0 and 2*b<sigma(b)) or (n mod 2=1 and 2*b>sigma(b)) then
a:=[op(a), k]; break; fi; fi; od; od; print(op(a)); end: P(100);
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Paolo P. Lava, Aug 14 2024
STATUS
approved