A175459 a(1)=4. a(n) = a(n-1) + n, if a(n-1)+n is composite. Otherwise a(n) = a(n-1)*n.

4, 6, 9, 36, 180, 186, 1302, 1310, 11790, 11800, 11811, 11823, 11836, 11850, 11865, 11881, 11898, 11916, 11935, 11955, 11976, 11998, 12021, 12045, 12070, 12096, 12123, 12151, 12180, 12210, 378510, 378542, 378575, 378609, 378644, 378680

Offset

1,1

Comments

Each term is composite.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Maple

A175459 := proc(n) option remember; if n =1 then 4; else if isprime( procname(n-1)+n) then procname(n-1)*n; else procname(n-1)+n ; end if; end if; end proc:
seq(A175459(n), n=1..120) ; # R. J. Mathar, May 28 2010

Mathematica

nxt[{n_, a_}]:={n+1, If[CompositeQ[a+n+1], a+n+1, a(n+1)]}; NestList[nxt, {1, 4}, 40][[All, 2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 11 2019 *)

Crossrefs

Sequence in context: A291717 A303699 A292153 * A257652 A107665 A085733

Adjacent sequences: A175456 A175457 A175458 * A175460 A175461 A175462

Keyword

nonn

Author

Leroy Quet, May 20 2010

Extensions

More terms from R. J. Mathar, May 28 2010

Status

approved