OFFSET
1,2
EXAMPLE
a(4)=4 because the divisors of 7#-1 = 209 are {1, 11, 19, 209}.
MAPLE
seq(numtheory[tau](mul(ithprime(k), k=1..n)-1), n=1..30);
MATHEMATICA
Map[DivisorSigma[0, #] &, -1 + FoldList[Times, Prime@ Range@ 30] ] (* Michael De Vlieger, Oct 25 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 23 2023
STATUS
approved