A076561 a(1)=2; a(n>1)= greatest prime divisor of {a(n-1) + n}.

2, 2, 5, 3, 2, 2, 3, 11, 5, 5, 2, 7, 5, 19, 17, 11, 7, 5, 3, 23, 11, 11, 17, 41, 11, 37, 2, 5, 17, 47, 13, 5, 19, 53, 11, 47, 7, 5, 11, 17, 29, 71, 19, 7, 13, 59, 53, 101, 5, 11, 31, 83, 17, 71, 7, 7, 2, 5, 2, 31, 23, 17, 5, 23, 11, 11, 13, 3, 3, 73, 3, 5, 13, 29, 13, 89, 83, 23, 17

Offset: 1

Author

Zak Seidov, Oct 19 2002

Keywords

• easy
• nonn

Links

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

Crossrefs

Cf. A076560 (a(1)=1).

Programs

Mathematica

nxt[{n_,a_}]:={n+1,Max[FactorInteger[a+n+1][[All,1]]]}; NestList[nxt,{1,2},80][[All,2]] (* Harvey P. Dale, Jan 06 2023 *)

PARI

lista(nn) = {v = vector(nn); v[1] = 2; for (n=2, nn, f = factor(v[n-1]+n); v[n] = f[#f~, 1];); v;} \\ Michel Marcus, Aug 08 2014

Extensions

Definition clarified by Harvey P. Dale, Jan 06 2023