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A306591 a(n) is the denominator of 1/2 - 1/(prime(n)+1), where prime(n) is the n-th prime. 1
6, 4, 3, 8, 12, 7, 9, 20, 24, 15, 32, 19, 21, 44, 48, 27, 60, 31, 68, 72, 37, 80, 84, 45, 49, 51, 104, 108, 55, 57, 128, 132, 69, 140, 75, 152, 79, 164, 168, 87, 180, 91, 192, 97, 99, 200, 212, 224, 228, 115, 117, 240, 121, 252, 129, 264, 135, 272, 139, 141, 284, 147, 308, 312, 157 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..65.

Nitya Mani and Simon Rubinstein-Salzedo, Diophantine Tuples over Zp, arXiv:1902.09048 [math.NT], 2019. See Lemma 3.3. p. 4.

PROG

(PARI) a(n) = denominator(1/2 - 1/(prime(n)+1));

(Python)

from sympy import prime

from fractions import Fraction

def a(n): return (Fraction(1, 2) - Fraction(1, (prime(n)+1))).denominator

print([a(n) for n in range(1, 66)]) # Michael S. Branicky, Jun 04 2021

CROSSREFS

Cf. A236965 (numerators).

Cf. A145979 (denominator of 1/2 - 1/(n+1)).

Sequence in context: A195475 A321786 A188725 * A268817 A020794 A268818

Adjacent sequences:  A306588 A306589 A306590 * A306592 A306593 A306594

KEYWORD

nonn,frac

AUTHOR

Michel Marcus, Feb 26 2019

STATUS

approved

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Last modified September 19 22:06 EDT 2021. Contains 347576 sequences. (Running on oeis4.)