A322947 Numbers k such that 2k + 1 is a palindromic prime.

1, 2, 3, 5, 50, 65, 75, 90, 95, 156, 176, 186, 191, 363, 378, 393, 398, 459, 464, 5150, 5250, 5300, 5655, 5705, 6210, 6360, 6410, 6665, 6915, 6965, 7170, 7370, 7725, 7775, 8030, 8180, 8280, 8330, 8735, 8985, 9090, 9240, 9695, 9945, 9995, 15051, 15101, 15201, 15351, 15401, 15506, 15756

Offset

1,2

Links

Daniel Starodubtsev, Table of n, a(n) for n = 1..1000

Formula

a(n) = (A002385(n+1) - 1)/2. - Rémy Sigrist, Jan 01 2019

Example

5 is in the sequence, because 2 * 5 + 1 = 11 is a prime palindrome.

Mathematica

Select[Range[16000], And[PrimeQ@ #, PalindromeQ@ #] &[2 # + 1] &] (* Michael De Vlieger, Jan 01 2019 *)

Prog

(PARI) isok(n) = my(p=2*n+1, d=digits(p)); isprime(p) && (Vecrev(d) == d); \\ Michel Marcus, Jan 01 2019

Crossrefs

Cf. A002385 (palindromic primes).

Sequence in context: A060380 A062608 A041791 * A056720 A100850 A309607

Adjacent sequences: A322944 A322945 A322946 * A322948 A322949 A322950

Keyword

nonn,base

Author

Daniel Starodubtsev, Dec 31 2018

Status

approved