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.

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

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