A131199 a(0)=2. For n>=1, a(n) = a(n-1) + n if a(n-1) is composite; a(n) = a(n-1)*n if a(n-1) is prime.

2, 2, 4, 7, 28, 33, 39, 46, 54, 63, 73, 803, 815, 828, 842, 857, 13712, 13729, 247122, 247141, 4942820, 4942841, 4942863, 4942886, 4942910, 4942935, 4942961, 4942988, 4943016, 4943045, 4943075, 4943106, 4943138, 4943171, 4943205, 4943240

Offset

0,1

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Maple

a[0]:=2: for n to 30 do if isprime(a[n-1])=false then a[n]:=a[n-1]+n else a[n]:=a[n-1]*n end if end do: seq(a[n], n=0..30); # Emeric Deutsch, Oct 24 2007
A131199 := proc(n) option remember ; if n = 0 then 2 ; else if isprime(A131199(n-1)) then n*A131199(n-1) ; else n+A131199(n-1) ; fi ; fi ; end: seq(A131199(n), n=0..80) ; # R. J. Mathar, Oct 30 2007

Mathematica

Transpose[NestList[If[PrimeQ[Last[#]], {First[#]+1, (First[#]+1)Last[#]}, {First[#]+1, Total[#]+1}]&, {0, 2}, 40]][[2]] (* Harvey P. Dale, Jun 02 2012 *)

Crossrefs

Cf. A083524.

Sequence in context: A238184 A340333 A065844 * A112059 A093094 A045777

Adjacent sequences: A131196 A131197 A131198 * A131200 A131201 A131202

Keyword

nonn

Author

Leroy Quet, Oct 21 2007

Extensions

More terms from Emeric Deutsch and R. J. Mathar, Oct 24 2007

Status

approved