A056144 a(1) = 1, a(m+1) = Sum_{k=1..m} gcd(m, a(k)).

1, 1, 2, 3, 5, 9, 11, 7, 9, 27, 15, 21, 25, 13, 27, 49, 17, 33, 59, 19, 33, 69, 53, 45, 47, 61, 39, 117, 47, 29, 89, 31, 33, 161, 51, 75, 105, 37, 57, 159, 65, 41, 135, 43, 85, 251, 91, 139, 89, 127, 127, 171, 113, 157, 199, 131, 93, 227, 87, 117, 185, 121, 123, 227, 65

Offset

1,3

Comments

From Ivan Neretin, Apr 06 2016: (Start)

a(n) >= n-1.

All terms except a(3) = 2 are odd.

For all n of the form 2^k+1 except 3, a(n) = n.

(End)

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Example

a(7) = gcd(6,1) + gcd(6,1) + gcd(6,2) + gcd(6,3) + gcd(6,5) + gcd(6,9) = 1 + 1 + 2 + 3 + 1 + 3 = 11.

Mathematica

Fold[Append[#1, Total@GCD[#1, #2]] &, {1}, Range@64] (* Ivan Neretin, Apr 06 2016 *)

Crossrefs

Cf. A093820.

Sequence in context: A262990 A058108 A174512 * A284626 A284847 A186776

Adjacent sequences: A056141 A056142 A056143 * A056145 A056146 A056147

Keyword

easy,nonn

Author

Leroy Quet, Aug 04 2000

Status

approved