A271531 a(1) = 1; thereafter a(n) is the LCM of all 0 < m < n for which n == a(m) (mod m).

1, 1, 2, 1, 12, 1, 30, 3, 28, 9, 24, 5, 132, 3, 26, 7, 420, 1, 360, 3, 4, 5, 1680, 253, 84, 15, 440, 117, 1020, 7, 42, 15, 28, 725, 2376, 1, 47880, 3, 2960, 1, 29640, 155, 120, 21, 476, 11781, 11040, 1, 2640, 3, 1288, 5, 300, 13, 144, 285, 2860, 7, 4200, 1

Offset

1,3

Links

Peter Kagey, Table of n, a(n) for n = 1..10000

Example

a(1) = 1 by definition.
a(2) = 1, because 2 == a(1) (mod 1);
a(3) = 2, because 3 == a(1) (mod 1), and 3 == a(2) (mod 2): lcm(1, 2) = 2;
a(4) = 1, because 4 == a(1) (mod 1);
a(5) = 12, because 5 == k (mod k) for 0 < k < 5: lcm(1, 2, 3, 4) = 12.

Prog

(PARI) lista(nn) = {va = vector(nn); va[1] = 1; print1(va[1], ", "); for (n=2, nn, new = 1; for (k=1, n-1, if (Mod(va[k], k) == Mod(n, k), new = lcm(new, k); ); ); va[n] = new; print1(va[n], ", "); ); } \\ Michel Marcus, Mar 13 2018

Crossrefs

Sequence in context: A105608 A051190 A072512 * A118588 A259633 A174500

Adjacent sequences: A271528 A271529 A271530 * A271532 A271533 A271534

Keyword

nonn

Author

Peter Kagey, Apr 09 2016

Status

approved