A100996 a(1) = 1; a(n) is smallest positive integer such that a(n)*a(n-1)+1 is coprime to n.

1, 2, 2, 1, 1, 4, 1, 2, 2, 1, 1, 4, 1, 2, 3, 2, 1, 4, 1, 2, 2, 1, 1, 4, 2, 1, 1, 2, 1, 6, 1, 2, 2, 1, 1, 4, 1, 2, 2, 1, 1, 4, 1, 2, 3, 2, 1, 4, 1, 2, 2, 1, 1, 4, 2, 1, 1, 2, 1, 6, 1, 2, 2, 1, 1, 4, 1, 2, 2, 1, 1, 4, 1, 2, 3, 2, 1, 4, 1, 2, 2, 1, 1, 4, 2, 1, 1, 2, 1, 6, 3, 2, 2, 1, 1, 4, 1, 2, 2, 1, 1, 4, 1, 2, 5

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Mathematica

a[1] = 1; a[n_] := a[n] = Block[{k = 1}, While[ GCD[k*a[n - 1] + 1, n] != 1, k++ ]; k]; Table[ a[n], {n, 105}]

Prog

(PARI)
up_to = 65537;
A100996list(up_to_n) = { my(v=vector(up_to_n)); v[1] = 1; for(n=2, #v, for(k=1, oo, if(1==gcd(1+(k*v[n-1]), n), v[n] = k; break))); (v); };
v100996 = A100996list(up_to);
A100996(n) = v100996[n]; \\ Antti Karttunen, Jan 17 2025

Crossrefs

Sequence in context: A319700 A279104 A165509 * A232504 A292201 A343070

Adjacent sequences: A100993 A100994 A100995 * A100997 A100998 A100999

Keyword

nonn

Author

Leroy Quet, Jan 13 2005

Extensions

More terms from Robert G. Wilson v, Feb 11 2005

Status

approved