OFFSET
0,3
FORMULA
Let b(n) = Pochhammer(n+1,n)/denominator(Bernoulli(n)) then a(2*n) = b(2*n) for n >= 0 and 2*a(2*n+1) = b(2*n+1) for n >= 1 by the von Staudt-Clausen theorem.
MAPLE
a := proc(n) numtheory[divisors](n); map(i->i+1, %);
iquo(mul(4*k+2, k in (0..n-1)), mul(k, k in select(isprime, %))) end:
seq(a(n), n=0..19);
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Feb 14 2016
STATUS
approved