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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A091089 Numbers which form a prime by appending a 3-digit odd number and form no primes by appending any 1- or 2-digit odd number not beginning with 0. 7
 16557, 16718, 26378, 35921, 46524, 46867, 50018, 55187, 58374, 58452, 60850, 63714, 68771, 71299, 78035, 78269, 81661, 84213, 89052, 90157, 95490, 97080, 102892, 105690, 108682, 115558, 115994, 116138, 116305, 121097, 128192, 131194 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Many numbers become prime by appending a one-digit odd number. Some numbers (such as 20, 32, 51, etc.) require a 2-digit odd number (A032352 has these). In the first 100000 values of n there are only 22 that require a 3-digit odd number. LINKS Robert Price, Table of n, a(n) for n = 1..23419 Index entries for primes involving decimal expansion of n EXAMPLE a(1)=16557 because 16557 is first number which requires a 3-digit odd number be appended to it to form a prime. 165571, 165573, 165575, ..., 165579, 1655711, 1655713, ..., 1655799 are all nonprime numbers. 16557103 is the first prime formed by appending odd numbers to 16657. a(2) = 16718 because 16718111 is the first prime formed by appending odd numbers to 16718. CROSSREFS Cf. A032352 (a(n) requires at least a 2-digit odd number), A068695 (minimum odd number that must be appended to n to form a prime). Sequence in context: A253956 A253963 A253759 * A109028 A193244 A240901 Adjacent sequences: A091086 A091087 A091088 * A091090 A091091 A091092 KEYWORD base,nonn AUTHOR Chuck Seggelin (barkeep(AT)plastereddragon.com), Dec 18 2003 EXTENSIONS Definition edited by N. J. A. Sloane, Nov 08 2020 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 16 23:10 EDT 2024. Contains 371755 sequences. (Running on oeis4.)