OFFSET
1,4
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..99
Hisanori Mishima, Factorizations of many number sequences
R. G. Wilson v, Explicit factorizations
EXAMPLE
a(4)=2 because 2*3*5*7 - 1 = 209 = 11*19
MATHEMATICA
a[q_] := Module[{x, n}, x=FactorInteger[Product[Table[Prime[i], {i, q}][[j]], {j, q}]-1]; n=Length[x]; Sum[Table[x[[i]][[2]], {i, n}][[j]], {j, n}]]
PrimeOmega[#] & /@ (FoldList[Times, Prime[Range[81]]] - 1) (* Harvey P. Dale, Mar 11 2017 *)
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Arne Ring (arne.ring(AT)epost.de), May 30 2000
EXTENSIONS
More terms from Robert G. Wilson v, Mar 24 2001
a(42)-a(81) from Charles R Greathouse IV, May 07 2011
a(82)-a(87) from Amiram Eldar, Oct 03 2019
STATUS
approved