A067533 Numbers k such that both k - tau(k) and k + tau(k) are prime where tau(k) = A000005(k).

5, 15, 27, 33, 57, 93, 105, 165, 177, 189, 231, 237, 245, 267, 275, 285, 345, 375, 393, 425, 453, 555, 567, 573, 597, 609, 637, 651, 687, 723, 833, 933, 1005, 1025, 1095, 1167, 1209, 1221, 1227, 1293, 1311, 1431, 1445, 1479, 1491, 1527, 1551, 1563, 1573

Offset

1,1

Links

Marius A. Burtea, Table of n, a(n) for n = 1..1128

Example

57 is a term as tau(57) = 4 and 57-4 = 53 and 57+4 = 61 are both primes.

Prog

(PARI) isok(n) = my(nd = numdiv(n)); isprime(n-nd) && isprime(n+nd); \\ Michel Marcus, Oct 12 2018

Crossrefs

Intersection of A067531 and A067532.

Sequence in context: A147426 A100437 A339567 * A110343 A146060 A076843

Adjacent sequences: A067530 A067531 A067532 * A067534 A067535 A067536

Keyword

easy,nonn

Author

Amarnath Murthy, Feb 17 2002

Extensions

More terms from Sascha Kurz, Mar 19 2002

Offset corrected by Alois P. Heinz, Oct 10 2018

Name changed by David A. Corneth, Oct 12 2018

Status

approved