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A366811
The number of divisors of prime(n)#+1 where p# is the product of all the primes from 2 to p inclusive.
1
2, 2, 2, 2, 2, 2, 4, 8, 4, 4, 8, 2, 8, 8, 4, 8, 16, 16, 4, 4, 16, 4, 8, 4, 16, 8, 4, 16, 16, 8, 8, 32, 8, 64, 4, 8, 4, 32, 16, 16, 4, 64, 8, 16, 8, 32, 64, 128, 4, 64, 8, 32, 8, 16, 4, 64, 32, 16, 32, 8, 32, 32, 32, 8, 8, 32, 32, 64, 8, 16, 16, 128, 32, 8, 16
OFFSET
0,1
FORMULA
a(n) = sigma0(prime(n)#+1) = A000005(A006862(n)).
EXAMPLE
a(6)=4 because the divisors of 13#+1 = 30031 are {1, 59, 509, 30031}.
MAPLE
seq(numtheory[tau](mul(ithprime(k), k=1..n)+1), n=0..30);
MATHEMATICA
Map[DivisorSigma[0, #] &, 1 + FoldList[Times, 1, Prime@ Range@ 19] ] (* Michael De Vlieger, Oct 25 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 23 2023
STATUS
approved