Sum Of (m/k), Over Some Divisors k
Leroy Quet
qq-quet at mindspring.com
Thu Apr 29 16:53:07 CEST 2004
An idea for a family of sequences:
Sometimes interesting sequences result if we sum, not over k (k being the
positive diuvisors of m), but over the (m/k)'s.
For example, if we take
a(m) = sum{k|m,k=prime power>1} (m/k),
we get (warning: figured by hand):
0, 1, 1, 3, 1, 5, 1, 7, 4, 7, 1, 13,...
(Also, a(m) = sum{j|m} phi(m/j) b(j), where b(j) is the sum of the
prime-factorization exponents of j.)
(Summing over just the primes gets sequence A069359.)
And 2 interesting recursively generated sequences are:
(Again, sequences figured by hand.)
c(1) = 1;
c(m) = sum{k|m, k is among {c(1),c(2),...,c(m-1)}} (m/k)
1, 2, 3, 6, 5, 12, 7, 12, 12, 17, 11, 25,...
f(1) = 1;
f(m) = sum{k|m, k not among {f(1),f(2),...,f(m-1)}} (m/k)
1, 1, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7,...
If we replace the (m/k) with k in the sequences {c(m)} and {f(m)},
however, then we would simply get the relatively uninteresting sequences
{1,1,1,1,...} and {1,2,3,4,5,6,...}.
Neither {a(m)}, {c(m)}, nor {f(m)} is in the EIS, it seems (if I
calculated by hand correctly).
thanks,
Leroy Quet
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