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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 (list; graph; refs; listen; history; text; internal format)
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

M. F. Hasler, Table of n, a(n) for n = 1..14868.

Eric Angelini, A fractal sequence with prime sums

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

Adjacent sequences:  A133179 A133180 A133181 * A133183 A133184 A133185

KEYWORD

nonn,look

AUTHOR

Eric Angelini, Oct 11 2007

STATUS

approved

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Last modified July 10 16:22 EDT 2020. Contains 335577 sequences. (Running on oeis4.)