A079797 Products of two primes p and q such that (p*q)^2 + p^2 - q^2 and (p*q)^2 - p^2 + q^2 are both prime.

6, 14, 22, 33, 35, 38, 62, 69, 74, 85, 115, 119, 146, 159, 214, 219, 237, 267, 301, 335, 339, 469, 511, 519, 537, 542, 559, 566, 573, 591, 597, 634, 718, 721, 737, 794, 803, 851, 878, 917, 933, 1003, 1007, 1042, 1059, 1099, 1219, 1226, 1241, 1271, 1294, 1299

Offset

1,1

Comments

The two primes generated from p and q are sometimes called flip-flap twin primes. There is probably an infinity of them.

Links

Table of n, a(n) for n=1..52.

Example

a(2) = 14 since (2*7)^2 + 2^2 - 7^2 = 151 and (2*7)^2 - 2^2 + 7^2 = 241 are both primes.

Crossrefs

Sequence in context: A017137 A211998 A190522 * A093380 A123228 A015832

Adjacent sequences: A079794 A079795 A079796 * A079798 A079799 A079800

Keyword

easy,nonn

Author

Olivier Gérard, Feb 19 2003

Status

approved