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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A108844 Palindromic primes in which all internal digits are 7. 9
 373, 1777771, 377777777777773, 1777777777777777777777777777777777777777777777771, 3777777777777777777777777777777777777777777777777777773, 377777777777777777777777777777777777777777777777777777777777777777773 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(13) has 1003 digits. - Michael S. Branicky, Jan 27 2023 LINKS Michael S. Branicky, Table of n, a(n) for n = 1..12 MATHEMATICA Union[Flatten[Table[Select[Table[FromDigits[Join[{i}, PadRight[{}, n, 7], {i}]], {n, 100}], PrimeQ], {i, 1, 9, 2}]]] (* Harvey P. Dale, Nov 22 2012 *) PROG (PARI) n10np1(n, d) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+floor(10^x*d/9)*10+k; if(isprime(y), print1(y", ")) ) ) } (Python) from sympy import isprime from itertools import count, islice def agen(): yield from (t for i in count(1) for f in "1379" if isprime(t:=int(f + "7"*i + f))) print(list(islice(agen(), 12))) # Michael S. Branicky, Jan 27 2023 CROSSREFS Similar sequences for digit d: A108845 (d=1), A108846 (d=2), A108841 (d=4), A108842 (d=5), A108843 (d=6), A108847 (d=8). Sequence in context: A226850 A208834 A171216 * A025336 A025328 A045284 Adjacent sequences: A108841 A108842 A108843 * A108845 A108846 A108847 KEYWORD easy,nonn,base AUTHOR Cino Hilliard, Jul 11 2005 EXTENSIONS Name changed by Arkadiusz Wesolowski, Sep 07 2011 One more term (a(6)) added by Harvey P. Dale, Nov 22 2012 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.

Last modified April 23 08:10 EDT 2024. Contains 371905 sequences. (Running on oeis4.)