login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A028978 Product of prime and previous prime is palindromic. 3
3, 11, 19, 193, 1061, 1934071 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
No further terms < 4.5*10^8.
No further terms < 3.7*10^10. - Michael S. Branicky, Mar 11 2021
No further terms < 5.7*10^11. - Jon E. Schoenfield, Mar 13 2021
LINKS
EXAMPLE
19 belongs to this sequence as 17*19 = 323.
MATHEMATICA
p=2; t={}; Do[q=NextPrime[p]; If[Reverse[x=IntegerDigits[p*q]]==x, AppendTo[t, q]]; p=q, {n, 150000}]; t (* Jayanta Basu, Jun 05 2013 *)
Select[Partition[Prime[Range[150000]], 2, 1], PalindromeQ[Times@@#]&] [[All, 2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 26 2020 *)
PROG
(Python)
from sympy import nextprime
def ispal(n): s = str(n); return s == s[::-1]
def aupto(lim):
prevp, p, alst = 2, 3, []
while p < lim:
if ispal(p * prevp): alst.append(p)
prevp, p = p, nextprime(p)
return alst
print(aupto(2*10**6)) # Michael S. Branicky, Mar 11 2021
CROSSREFS
Intersection of A006094 and A002113.
Sequence in context: A192591 A075226 A192598 * A082628 A279257 A166096
KEYWORD
nonn,base,more
AUTHOR
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 18 21:02 EDT 2024. Contains 370951 sequences. (Running on oeis4.)