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 A342567 a(n) = (prime(n)^2 - prime(n-1)*prime(n+1))/2, n >= 3. 2
 2, -3, 15, -9, 21, -15, -11, 64, -56, 49, 45, -39, -35, 18, 124, -116, 79, 75, -140, 91, -71, -65, 210, 105, -99, 111, -105, -537, 663, -119, 280, -546, 606, -296, 18, 175, -155, 18, 364, -714, 774, -189, 201, -983, 72, 916, 231, -225, -221, 484, -954, 532, 18, 18 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 LINKS Hugo Pfoertner, Table of n, a(n) for n = 3..10000 FORMULA a(n) = A056221(n-1)/2 for n >= 3. MATHEMATICA a[n_]:=(Prime[n]^2 - Prime[n-1]*Prime[n+1])/2; Array[a, 54, 3] (* Stefano Spezia, Jul 15 2024 *) PROG (PARI) forprime(p=5, 265, my(pp=precprime(p-1), pn=nextprime(p+1)); print1((p^2-pp*pn)/2, ", ")) (Python) from primesieve.numpy import n_primes primesarray = numpy.array(n_primes(10005, 1)) for i in range (2, 10003): print(((primesarray[i]**2)-(primesarray[i-1]*primesarray[i+1]))//2) # Karl-Heinz Hofmann, Jun 20 2021 CROSSREFS Cf. A056221. Sequence in context: A266618 A082572 A075244 * A088030 A101047 A251618 Adjacent sequences: A342564 A342565 A342566 * A342568 A342569 A342570 KEYWORD sign,easy AUTHOR Hugo Pfoertner, Jun 20 2021 STATUS approved

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Last modified August 10 22:52 EDT 2024. Contains 375059 sequences. (Running on oeis4.)