OFFSET
1,3
LINKS
Reinhard Zumkeller, p(n)! - p(n)# + 1.
MATHEMATICA
Module[{nn=15, pr, pm}, pr=Prime[Range[nn]]!; pm=FoldList[Times, Prime[Range[nn]]]; DivisorSigma[1, #[[1]]-#[[2]]+1&/@Thread[{pr, pm}]]] (* Harvey P. Dale, Dec 18 2022 *)
PROG
(PARI) a(n) = sigma(prime(n)! - factorback(primes(n)) + 1); \\ Jinyuan Wang, Dec 28 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Feb 20 2005
STATUS
approved