A129090 a(1)=1; a(n) = gcd(a(n-1), n) + lcm(a(n-1), n).

1, 3, 6, 14, 71, 427, 434, 1738, 15643, 156431, 156442, 938654, 12202503, 170835043, 2562525646, 20500205170, 348503487891, 2091020927349, 39729397619632, 198646988098164, 1390528916687151, 30591636167117323, 703607631843698430

Offset: 1

Author

Leroy Quet, Mar 29 2007

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..498

Crossrefs

Cf. A129091.

Programs

Maple

a[1]:=1: for n from 2 to 30 do a[n]:=gcd(a[n-1],n)+lcm(a[n-1],n) od: seq(a[n],n=1..27); # Emeric Deutsch, Apr 13 2007

Mathematica

k = 1; Do[Print[k]; k = GCD[k, n] + LCM[k, n], {n, 2, 30}] (* Ryan Propper, Apr 07 2007 *)
nxt[{n_,a_}]:={n+1,GCD[a,n+1]+LCM[a,n+1]}; NestList[nxt,{1,1},30][[All,2]] (* Harvey P. Dale, Apr 19 2022 *)

Extensions

More terms from Ryan Propper and Emeric Deutsch, Apr 07 2007