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 A128287 Nonprime numbers n such that n divides A014137(n) = Partial sums of Catalan numbers (A000108). 1
 1, 8, 133, 49378 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Prime p divides A014137(p) for p = {2, 3, 5, 11, 17, 23, 29, 41, 47, 53, 59, 71, 83, 89, 101, ...} = A045309 Primes congruent to {0, 2} mod 3 = A045309 Primes p such that x^3 = n (integer) has only one solution mod p. a(5) > 5000000. - Chai Wah Wu, Nov 13 2014 LINKS EXAMPLE A014137(n) begins {1, 2, 4, 9, 23, 65, 197, 626, 2056, 6918, 23714, 82500, ...}. Thus a(1) = 1 because 1 is nonprime and divides A014137(1) = 2. a(2) = 8 because 8 is nonprime and divides A014137(8) = 2056 and A014137(n) is not divisible by any nonprime n for 1

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Last modified May 26 09:37 EDT 2020. Contains 334620 sequences. (Running on oeis4.)