A028888 Smaller of two successive primes with a palindromic product.

2, 7, 17, 191, 1051, 1934063

Offset

1,1

Comments

No further terms less than 1.38 * 10^10. - Michael S. Branicky, Feb 07 2021

Links

Table of n, a(n) for n=1..6.

Patrick De Geest, More palindromic products of integer sequences

Example

17 is in the sequence because 17 * 19 = 323.
19 is not in the sequence because 19 * 23 = 437.

Mathematica

p = 2; t = {}; Do[q = NextPrime[p]; If[Reverse[x = IntegerDigits[p * q]] == x, AppendTo[t, p]]; p = q, {n, 150000}]; t (* Jayanta Basu, Jun 05 2013 *)
Prime[#]&/@Flatten[Position[Times@@@Partition[Prime[Range[1934100]], 2, 1], _?(PalindromeQ[#] &)]] (* Harvey P. Dale, May 14 2019 *)

Prog

(Python)
from sympy import nextprime
def ispal(n): s = str(n); return s == s[::-1]
p, q = 2, 3
while True:
  if ispal(p*q): print(p)
  p, q = q, nextprime(q) # Michael S. Branicky, Feb 07 2021

Crossrefs

Cf. A028978, A028979.

Sequence in context: A122382 A025554 A285810 * A082627 A160617 A279334

Adjacent sequences: A028885 A028886 A028887 * A028889 A028890 A028891

Keyword

nonn,base,more

Author

Patrick De Geest

Extensions

Edited by N. J. A. Sloane, May 04 2007

Status

approved