A383489 a(n) is the number of divisors d_i(m) for which a divisor d_j(m) exists such that d_i(m) < d_j(m) < sigma(d_i(m)) where m = A383488(n).
1, 1, 1, 4, 2, 5, 3, 2, 6, 2, 1, 7, 2, 1, 8, 1, 6, 7, 1, 6, 8, 1, 2, 1, 1, 1, 8, 1, 4, 1, 11, 4, 1, 7, 1, 6, 11, 5, 1, 6, 8, 3, 11, 1, 1, 3, 13, 1, 1, 10, 1, 5, 5, 6, 3, 9, 12, 4, 1, 7, 1, 6, 4, 1, 15, 1, 13, 1, 1, 4, 11, 1, 10, 1, 6, 11, 1, 1, 1, 14, 4, 2, 13
Offset: 1
Keywords
Examples
The a(4) = 4 divisors d_i(A383488(4)) = d_i(24) are 4, 6, 8 and 12 because sigma(4) = 7 > 6, sigma(6) = 12 > 8, sigma(8) = 15 > 12 and sigma(12) = 28 > 24.
Links
- Felix Huber, Table of n, a(n) for n = 1..10000
Programs
-
Maple
with(NumberTheory): A383488:=proc(n) option remember; local k,i,L; if n=1 then 12 else for k from procname(n-1)+1 do L:=Divisors(k); for i to nops(L)-1 do if sigma(L[i])>L[i+1] then return k fi od od fi; end proc; A383489:=proc(n) local a,i,L; L:=Divisors(A383488(n)); a:=0; for i to nops(L)-1 do if sigma(L[i])>L[i+1] then a:=a+1 fi od; return a end proc; seq(A383489(n),n=1..83);