OFFSET
1,1
COMMENTS
Note that the first 7 terms are prime numbers. See also the sum of Omega (A022559).
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..5000
FORMULA
a(n+1) = a(n) + 2*A001222(n), with a(1)=3.
EXAMPLE
a(2)=a(1)+2*Omega(1)=3+2=5;
a(3)=a(2)+2*Omega(2)=5+2=7;
a(4)=a(3)+2*Omega(3)=7+4=11;
MATHEMATICA
Omega = Plus @@ Sum[Transpose[FactorInteger[ # ]][[2]]] &; FoldList[Plus, 3, 2Map[Omega, Range[2, 200]]]
nxt[{n_, a_}]:={n+1, a+2PrimeOmega[n]}; Rest[Transpose[NestList[nxt, {1, 3}, 60]][[2]]] (* Harvey P. Dale, Mar 13 2016 *)
Fold[Append[#1, Last[#1] + 2 PrimeOmega[#2]] &, {3}, Range[2, 59]] (* Michael De Vlieger, Oct 16 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Carlos Alves, Nov 12 2006
STATUS
approved