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 A320624 a(n) = (A006134((prime(n)-1)/2) - Legendre(prime(n), 3))/prime(n). 1
 1, 2, 4, 32, 98, 1034, 3484, 41582, 1868198, 6751460, 330246410, 4522217312, 16829506610, 235344648416, 12559206444236, 683534482499900, 2599887148071402, 144419015585768252, 2117118216002111198, 8120930597438173620 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 COMMENTS a(n) is always an integer. Primes p such that p^2 divides A006134((p-1)/2) - Legendre(p, 3) are p = 103, ... What's the next? LINKS Table of n, a(n) for n=2..21. FORMULA a(2) = (binomial(0, 0) + binomial(2, 1))/3 = 3/3 = 1. a(3) = (binomial(0, 0) + binomial(2, 1) + binomial(4, 2) + 1)/5 = 10/5 = 2. a(4) = (binomial(0, 0) + binomial(2, 1) + binomial(4, 2) + binomial(6, 3) - 1)/7 = 28/7 = 4. PROG (PARI) A006134(n) = sum(k=0, n, binomial(2*k, k)) a(n) = my(p=prime(n)); (A006134((p-1)/2) - kronecker(p, 3))/p CROSSREFS Cf. A006134, A102283, A320626. Sequence in context: A197099 A009098 A192387 * A133127 A122693 A019060 Adjacent sequences: A320621 A320622 A320623 * A320625 A320626 A320627 KEYWORD nonn AUTHOR Jianing Song, Oct 18 2018 STATUS approved

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Last modified September 29 19:14 EDT 2023. Contains 365776 sequences. (Running on oeis4.)