A327447 a(n) = 4*p(n-1)*p(n+1) - p(n)^2, where p(k) = k-th prime.

31, 59, 171, 243, 579, 699, 1203, 1675, 2011, 3331, 3715, 4683, 5859, 6907, 8283, 9451, 12091, 12835, 14523, 17107, 17995, 21235, 24283, 26547, 29763, 32619, 33459, 36483, 42603, 43083, 52435, 54067, 62331, 61755, 70771, 73803, 78307, 84907, 89643, 93211, 103995, 103251, 113259, 114819, 126667, 132987, 141859

Offset

2,1

Comments

It follows from Sándor et al., Sect. VII.18(b) that a(n) > 0 for all n.

References

József Sándor, Dragoslav S. Mitrinovic, and Borislav Crstici, Handbook of Number Theory I, Springer Science & Business Media, 2005, Chapter VII, p. 247, section VII.18(b).

Links

Table of n, a(n) for n=2..48.

Mathematica

With[{p = Prime[Range[50]]}, 4 * p[[1;; -3]] * p[[3;; -1]] - p[[2;; -2]]^2] (* Amiram Eldar, Apr 25 2024 *)

Crossrefs

Cf. A309487, A324795.

Sequence in context: A039350 A043173 A043953 * A139954 A153636 A109840

Adjacent sequences: A327444 A327445 A327446 * A327448 A327449 A327450

Keyword

nonn

Author

N. J. A. Sloane, Sep 14 2019

Status

approved