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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
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
Sequence in context: A264090 A345283 A369750 * A297439 A168175 A164382
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.)