A133182 - OEIS

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, 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