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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
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
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

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Last modified April 16 23:10 EDT 2024. Contains 371755 sequences. (Running on oeis4.)