A308469 a(1) = 1, a(2)=2, a(n) = a(n-1) + gcd(a(n-2), n-2).

1, 2, 3, 5, 8, 9, 10, 13, 14, 15, 16, 21, 22, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 45, 46, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 93, 94, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113

Offset: 1

Author

Thomas Kerscher, May 29 2019

Keywords

• nonn

Comments

Apparently, the distinct values of a(n)-n for n > 7 correspond to A190894. - Rémy Sigrist, Jul 23 2019

Crossrefs

Cf. A106108, A190894.

Programs

Mathematica

a[1] = 1; a[2] = 2; a[n_] := a[n] = a[n-1] + GCD[a[n-2], n-2]; Array[a, 70] (* Amiram Eldar, Aug 01 2019 *)