A081518 Final term in row n of A081520.

1, 2, 6, 6, 20, 8, 42, 14, 24, 15, 110, 16, 156, 22, 30, 30, 272, 26, 342, 32, 48, 38, 506, 34, 120, 46, 78, 48, 812, 39, 930, 62, 81, 62, 110, 52, 1332, 70, 99, 65, 1640, 57, 1806, 78, 95, 86, 2162, 70, 336, 82, 135, 94, 2756, 80, 198, 96, 152, 110, 3422, 81, 3660, 118

Offset: 1

Author

Amarnath Murthy, Mar 27 2003

Keywords

• nonn

Comments

a(p) = p(p-1) if p is a prime.

a(p^k) = p (p^k - 1) if p is a prime and k >= 1. - Robert Israel, May 21 2015

Links

• Ivan Neretin, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A081519, A081520.

Programs

Maple

A:= n -> select(t->igcd(t,n)>1,[$1..n^2])[n-1]:
1, seq(A(n),n=2..100); # Robert Israel, May 21 2015

Mathematica

Table[Join[{1}, Select[Range[n^2], GCD[n, #] > 1 &, n - 1]][[-1]], {n, 1, 60}](* Ivan Neretin, May 21 2015 *)

Extensions

More terms from Ryan Propper, Nov 05 2005