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A322947 Numbers k such that 2k + 1 is a palindromic prime. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

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 A060085

Adjacent sequences:  A322944 A322945 A322946 * A322948 A322949 A322950

KEYWORD

nonn,base

AUTHOR

Daniel Starodubtsev, Dec 31 2018

STATUS

approved

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Last modified May 26 13:05 EDT 2019. Contains 323586 sequences. (Running on oeis4.)