A112337 a(1)=1, a(2) = 2. a(n) = a(n-2) + (largest prime dividing a(n-1)).

1, 2, 3, 5, 8, 7, 15, 12, 18, 15, 23, 38, 42, 45, 47, 92, 70, 99, 81, 102, 98, 109, 207, 132, 218, 241, 459, 258, 502, 509, 1011, 846, 1058, 869, 1137, 1248, 1150, 1271, 1191, 1668, 1330, 1687, 1571, 3258, 1752, 3331, 5083, 3354, 5126, 3587, 5337, 4180, 5356

Offset

1,2

Links

Ivan Neretin, Table of n, a(n) for n = 1..5000

Example

a(13) = a(11) + (largest prime dividing a(12)). a(12) is 38 and 19 is the largest prime dividing it. So a(13) = 23 + 19 = 42.

Mathematica

Nest[Append[#, FactorInteger[#[[-1]]][[-1, 1]] + #[[-2]]] &, {1, 2}, 51] (* Ivan Neretin, Jun 18 2018 *)

Prog

(MuPAD) A := array(1..100); A[1] := 1; A[2] := 2; for n from 3 to 100 do s := ifactor(A[n-1]); b := s[nops(s)-1]; A[n] := A[n-2] + b; print(A[n]); end_for; // Stefan Steinerberger, Dec 02 2005

Crossrefs

Cf. A078695, A006530.

Sequence in context: A284172 A230445 A125727 * A141804 A121368 A010073

Adjacent sequences: A112334 A112335 A112336 * A112338 A112339 A112340

Keyword

nonn

Author

Leroy Quet, Dec 01 2005

Extensions

More terms from Stefan Steinerberger, Dec 02 2005

Status

approved