A389676 - OEIS

A389676

a(n) = Min_{0<i<n} (prime(n-i) + prime(n+i)).

7, 10, 16, 20, 26, 32, 40, 48, 54, 62, 70, 78, 88, 96, 104, 114, 120, 130, 140, 150, 156, 166, 174, 182, 192, 202, 212, 220, 236, 244, 252, 264, 276, 286, 294, 306, 312, 330, 338, 350, 362, 372, 380, 392, 406, 420, 428, 438, 450, 462, 470, 480, 492, 510, 516

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OFFSET

2,1

LINKS

Table of n, a(n) for n=2..56.

Thomas Bloom, Problem #454, Erdős Problems.

P. Erdős, and R. L. Graham, Old and new problems and results in combinatorial number theory, Monographies de L'Enseignement Mathématique (1980).

Carl Pomerance, The prime number graph, Math. Comp. (1979), 399-408.

FORMULA

A conjecture of Pomerance: lim sup (a(n)-2*prime(n)) = oo.

Pomerance proved lim sup (a(n)-2*prime(n)) >= 2.

MATHEMATICA