A076056 - OEIS

A076056

Primes which when read backwards are composite numbers.

19, 23, 29, 41, 43, 47, 53, 59, 61, 67, 83, 89, 103, 109, 127, 137, 139, 163, 173, 193, 197, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 317, 331, 349, 367, 379, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Subsidiary sequences that could be added:(1) Start of the first occurrence of n consecutive primes in the above sequence. (2) Start of the first occurrence of n consecutive primes with digit reversal also a prime.

The subsidiary sequence (1) with the indices at which n>=2 consecutive primes are first found in this sequence is 1, 1, 4, 4, 4, 4, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, ... - R. J. Mathar, May 22 2009

Subsequence of A151768. - Reinhard Zumkeller, Jul 06 2009

LINKS

Anders Hellström, Table of n, a(n) for n = 1..10000

Anders Hellström, Sage program

MATHEMATICA

Select[Prime[Range[100]], !PrimeQ[FromDigits[Reverse[IntegerDigits[ # ]]]]&]

PROG

(Magma) [p: p in PrimesUpTo(500)|not IsPrime(Seqint(Reverse(Intseq(p))))]; // Vincenzo Librandi, Jun 03 2019

CROSSREFS

Cf. A076055.

Complement of A007500 with respect to A000040. [From Reinhard Zumkeller, Jul 06 2009]

Sequence in context: A151768 A270083 A286333 * A068654 A286415 A305835