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 A365780 Lexicographically earliest finite sequence of nonprime numbers such that a(n) + [the next digit] is a prime number. 2
 1, 4, 9, 8, 30, 10, 12, 14, 32, 50, 33, 40, 15, 20, 34, 35, 6, 16, 18, 51, 21, 22, 70, 36, 52, 72, 74, 54, 55, 42, 56, 38, 39, 24, 57, 25, 44, 90, 75, 45, 26, 58, 91, 60, 76, 77, 27, 28, 92, 93, 46, 78, 100, 94, 95, 62, 96, 102, 104, 98, 99, 48, 500, 300, 700, 105, 49, 400, 106, 108, 110, 301, 63, 80, 302, 501, 81, 82, 111, 200 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The sequence is finite. The last term is 200 as the next prime after 200 is 211 and so the first digit of any next term is too small to reach 211. - David A. Corneth, Sep 18 2023 LINKS Table of n, a(n) for n=1..80. EXAMPLE a(1) = 1 and 1 + 4 = 5 (prime); a(2) = 4 and 4 + 9 = 13 (prime); a(3) = 9 and 9 + 8 = 17 (prime); a(4) = 8 and 8 + 3 = 11 (prime); a(5) = 30 and 30 + 1 = 31 (prime); etc. PROG (PARI) sequence() = {my(res = List([1]), n = 700, leftover = vector(n, i, 1), proceed = 1); leftover[1] = 0; forprime(p = 2, n, leftover[p] = 0); while(proceed, for(i = 1, n, if(leftover[i] && isprime(res[#res] + digits(i)[1]), listput(res, i); leftover[i] = 0; next(2))); proceed = 0); res} \\ David A. Corneth, Sep 18 2023 CROSSREFS Cf. A365768, A365769, A365781. Sequence in context: A264090 A345283 A369750 * A297439 A168175 A164382 Adjacent sequences: A365777 A365778 A365779 * A365781 A365782 A365783 KEYWORD nonn,easy,base,fini,full AUTHOR Eric Angelini, Sep 18 2023 EXTENSIONS More terms from David A. Corneth, Sep 18 2023 STATUS approved

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Last modified April 12 07:22 EDT 2024. Contains 371623 sequences. (Running on oeis4.)