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 A210514 Prime numbers generated by concatenating k, k, and 9. 2
 229, 449, 11119, 14149, 22229, 28289, 31319, 37379, 44449, 49499, 52529, 56569, 67679, 70709, 71719, 80809, 86869, 89899, 94949, 95959, 1061069, 1101109, 1131139, 1151159, 1161169, 1191199, 1241249, 1251259, 1331339, 1401409, 1431439, 1481489, 1571579, 1601609 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This series is similar to A030458 and A052089. Base considered is 10. LINKS Michael S. Branicky, Table of n, a(n) for n = 1..10000 EXAMPLE For k=2, a(1)= 229. For k=4, a(2)= 449. For k=11, a(3)= 11119. For k=14, a(4)= 14149. MATHEMATICA Select[Table[FromDigits[Flatten[Join[IntegerDigits/@{n, n}, {9}]]], {n, 200}], PrimeQ] (* Harvey P. Dale, Apr 23 2015 *) PROG (Python) import numpy as np from functools import reduce def factors(n): return reduce(list.__add__, ([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0)) for i in range(1, 2000): p1=int(str(i)+str(i)+"1") if len(factors(p1))<3: print(p1, end=', ') (Python) from sympy import isprime from itertools import count, islice def agen(): yield from filter(isprime, (int(str(k)+str(k)+'9') for k in count(1))) print(list(islice(agen(), 34))) # Michael S. Branicky, Jul 26 2022 CROSSREFS Cf. A030458, A052089. Sequence in context: A139512 A142263 A142608 * A142665 A124684 A332740 Adjacent sequences: A210511 A210512 A210513 * A210515 A210516 A210517 KEYWORD base,nonn,easy AUTHOR Abhiram R Devesh, Jan 26 2013 EXTENSIONS a(27) and beyond from Michael S. Branicky, Jul 26 2022 STATUS approved

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Last modified February 25 11:09 EST 2024. Contains 370324 sequences. (Running on oeis4.)