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 A271531 a(1) = 1; thereafter a(n) is the LCM of all 0 < m < n for which n == a(m) (mod m). 3
 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 (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): 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

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Last modified November 21 15:52 EST 2018. Contains 317449 sequences. (Running on oeis4.)