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 A088629 Smallest number k not included earlier such that the concatenation n, k is a prime. 3
 1, 3, 7, 19, 9, 13, 27, 11, 29, 21, 17, 23, 61, 33, 31, 37, 41, 47, 49, 39, 43, 51, 57, 59, 79, 63, 53, 87, 69, 67, 81, 71, 73, 91, 83, 77, 93, 89, 103, 99, 113, 97, 117, 101, 119, 133, 111, 109, 121, 123, 131, 127, 129, 139, 147, 149, 107, 151, 141, 161, 153, 137, 179 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Another rearrangement of odd numbers not == 0 (mod 5). LINKS Michael S. Branicky, Table of n, a(n) for n = 1..10000 EXAMPLE a(4) = 19. Though 41, 43 and 47 are prime 1, 3 and 7 have been included earlier and also 49, 411, 413 and 417 are not prime hence 419 is the required prime. PROG (Python) from sympy import isprime from itertools import count, islice def agen(): aset, mink = set(), 1 for n in count(1): s, k = str(n), mink while k in aset or not isprime(int(s + str(k))): k += 1 while mink%5 == 0 or mink in aset: mink += 2 yield k; aset.add(k) print(list(islice(agen(), 63))) # Michael S. Branicky, Aug 20 2022 CROSSREFS Cf. A045572, A088630. Sequence in context: A361087 A212848 A217371 * A075609 A083439 A151858 Adjacent sequences: A088626 A088627 A088628 * A088630 A088631 A088632 KEYWORD base,nonn AUTHOR Amarnath Murthy, Oct 21 2003 EXTENSIONS More terms from Ray G. Opao, Aug 19 2004 STATUS approved

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Last modified April 14 00:20 EDT 2024. Contains 371652 sequences. (Running on oeis4.)