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A271530 a(1) = 1; thereafter a(n) is the product of all 0 < m < n for which n == a(m) (mod m). 2
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 (list; graph; refs; listen; history; text; internal format)
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: A059360 A279308 A108778 * A062763 A243147 A261407

Adjacent sequences:  A271527 A271528 A271529 * A271531 A271532 A271533

KEYWORD

nonn

AUTHOR

Peter Kagey, Apr 09 2016

STATUS

approved

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Last modified October 23 06:29 EDT 2018. Contains 316520 sequences. (Running on oeis4.)