OFFSET
1,2
COMMENTS
psi(n) is the sum of the totatives of n (A023896).
FORMULA
a(n) = Product_{i=1..n} A057661(i).
MATHEMATICA
FoldList[Times[#1, #2] &, Array[Sum[Total@ Select[Range@ d, CoprimeQ[#, d] &], {d, Divisors@ #}] &, 19]] (* Michael De Vlieger, Dec 27 2016 *)
PROG
(Magma) [&*[&+[&+[h: h in [1..d] | GCD(h, d) eq 1]: d in Divisors(k)]: k in [1..n]]: n in [1..1000]]
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Dec 27 2016
STATUS
approved