A392200 a(n) = gcd(A381466(n-1), n).

1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 1, 4, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 3, 1, 1, 6, 1, 4, 1, 1, 5, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 16, 1, 2, 1, 4, 1, 6, 1, 8, 1, 2, 1, 4, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 4, 1, 1, 15, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1

Offset

1,4

Comments

We conjecture that a(n) < log(n+1)/log(1.2).

Links

Sam Chapman, Table of n, a(n) for n = 1..10000

Example

a(1)=1, since A381466(0)=4 and gcd(4,1)=1.
a(4)=2, since A381466(4)=10 and gcd(10,4)=2.

Mathematica

s={4}; g={}; Do[G=GCD[s[[-1]], n]; AppendTo[s, If[G==1, s[[-1]]+n, n/G]]; AppendTo[g, G], {n, 86}]; g (* James C. McMahon, Mar 30 2026 *)

Prog

(PARI) lista(nn) = my(v = vector(nn)); v[1] = 4; for (n=2, nn, my(g=gcd(v[n-1], n-1)); if (g==1, v[n] = v[n-1] + n-1, v[n] = (n-1)/g); ); vector(#v, n, gcd(v[n], n)); \\ Michel Marcus, Mar 26 2026

Crossrefs

Cf. A381466.

Sequence in context: A122374 A261960 A010121 * A174726 A300239 A354364

Adjacent sequences: A392197 A392198 A392199 * A392201 A392202 A392203

Keyword

nonn,easy

Author

Sam Chapman, Mar 16 2026

Status

approved