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A110924
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a(1) = 1, a(2) = 2. a(n) is smallest positive integer not among earlier terms of the sequence where GCD(a(n),a(n-1)+a(n-2)) = 1.
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0
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1, 2, 4, 5, 7, 11, 13, 17, 19, 23, 25, 29, 31, 37, 3, 9, 35, 15, 21, 41, 27, 33, 43, 39, 45, 47, 49, 53, 55, 59, 61, 67, 51, 57, 65, 63, 69, 71, 73, 77, 79, 83, 85, 89, 91, 97, 75, 81, 95, 87, 93, 101, 99, 103, 105, 107, 109, 113, 115, 119, 121, 127, 111, 117, 125, 123, 129
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| 2 and 4 are the only even terms in the sequence. Is every odd positive integer in the sequence?
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EXAMPLE
| Of the positive integers not among the first 4 terms of the sequence, 7 is the smallest which is coprime to a(3) + a(4) = 4 + 5 = 9.
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PROG
| (PARI) { u=[2, 1]; c=3; s=u[1]+u[2]; m=Set(); m=setunion(m, [1]); m=setunion(m, [2]); print1(1, ", ", 2); for(k=1, 100, i=2; while(gcd(i, s)>1 || setsearch(m, i)!=0, i++); u[(c%2)+1] = i; c++; s=u[1]+u[2]; m=setunion(m, [i]); print1(i, ", ")) } (Klasen)
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CROSSREFS
| Sequence in context: A056527 A147991 A033160 * A192590 A028289 A039673
Adjacent sequences: A110921 A110922 A110923 * A110925 A110926 A110927
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Sep 23 2005
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EXTENSIONS
| More terms from Lambert Klasen (lambert.klasen(AT)gmx.net), Oct 25 2005
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