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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A032694 Exactly 4 digits from {1,2,3,4,5,6,7,8,9} can precede a(n) to form a prime. 1
 11, 19, 27, 31, 41, 47, 53, 67, 73, 87, 91, 97, 109, 129, 151, 153, 187, 203, 209, 217, 231, 243, 273, 283, 311, 323, 373, 389, 423, 433, 447, 451, 467, 481, 539, 549, 581, 583, 591, 607, 621, 623, 637, 643, 657, 659, 663, 669, 673, 677, 691, 693, 699, 753 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Daniel Starodubtsev, Table of n, a(n) for n = 1..10000 EXAMPLE If a(n) = 109 then we find '1'109, '3'109, '7'109 and '9'109 to be primes. PROG (Python) from sympy import isprime print([i for i in range(800) if [isprime(int(j + str(i))) for j in '123456789'].count(True) == 4]) # Daniel Starodubtsev, Apr 11 2020 CROSSREFS Sequence in context: A231012 A231007 A129916 * A004769 A224380 A125771 Adjacent sequences: A032691 A032692 A032693 * A032695 A032696 A032697 KEYWORD nonn,base AUTHOR Patrick De Geest, May 15 1998 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 June 2 18:52 EDT 2023. Contains 363100 sequences. (Running on oeis4.)