A271530 a(1) = 1; thereafter a(n) is the product of all 0 < m < n for which n == a(m) (mod m).

1, 1, 2, 1, 24, 1, 12, 3, 40, 1, 480, 7, 432, 15, 28, 13, 24, 11, 40320, 3, 1520, 9, 120, 85, 48, 21, 16, 345, 1452971520, 1, 8553600, 3, 56, 5, 44544, 1, 1161216, 3, 340, 13167, 155040, 13, 130636800, 15, 4736, 1, 36167040, 1075, 66960, 63, 40480, 1, 27456

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): 1 * 2 = 2;
a(4) = 1, because 4 == a(1) (mod 1);
a(5) = 24, because 5 == k (mod k) for 0 < k < 5: 1 * 2 * 3 * 4 = 24.

Mathematica

a = {1}; Do[AppendTo[a, Times @@ Flatten@ Position[MapIndexed[Mod[n, First@ #2] == Mod[#1, First@ #2] &, a], True]], {n, 2, 53}]; a (* Michael De Vlieger, Apr 09 2016 *)

Crossrefs

Cf. A269423, A271531.

Sequence in context: A279308 A345262 A108778 * A062763 A243147 A261407

Adjacent sequences: A271527 A271528 A271529 * A271531 A271532 A271533

Keyword

nonn

Author

Peter Kagey, Apr 09 2016

Status

approved