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URL: https://oeis.org/A133182

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A133182
A fractal sequence. Underline the first occurrence of "1", then the first occurrence of "2", the first "3", etc. The non-underlined terms are the sequence itself.
1
1, 2, 1, 2, 3, 4, 5, 1, 2, 6, 3, 4, 7, 8, 5, 9, 1, 2, 10, 6, 3, 4, 11, 7, 8, 5, 12, 13, 9, 1, 2, 14, 10, 6, 3, 4, 15, 16, 17, 11, 7, 8, 5, 18, 19, 20, 12, 13, 9, 1, 2, 21, 22, 23, 14, 24, 10, 6, 3, 4, 25, 26, 15, 27, 16, 28, 17, 11, 7, 8, 5, 29, 18, 30, 19, 20, 12, 13, 9, 1, 2, 31, 21, 22, 32
OFFSET
1,2
COMMENTS
For all [a,b,c] triples of consecutive terms where (a+b) is prime, do underline c. The non-underlined terms are the sequence itself.
LINKS
Eric Angelini, A fractal sequence with prime sums [Cached copy, with permission. Pdf file only, no color]
PROG
(PARI) A133182(find=2007, show=1, a=[1, 2], no=0, ni=2)={ while(a[ #a]!=find, a=concat(a, if(isprime(a[ #a]+a[ #a-1]), no++, a[ni++ ]))); if(show, a, #a)} /* use A133182(N) to get all terms up to first occurrence of N ; A133182(N, 0) to get only the index of that term */ \\ M. F. Hasler, Oct 17 2007
CROSSREFS
Sequence in context: A241416 A082854 A086742 * A071488 A318309 A114733
KEYWORD
nonn,look
AUTHOR
Eric Angelini, Oct 11 2007
STATUS
approved