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Search: id:A073895
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| A073895 |
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a(1)=1. a(n)=a(n-1)+k(n). If a(n-1) is nonprime, k(n) is the smallest composite not in the set {k(i),i<n}. If a(n-1) is prime, k(n) is the smallest prime not in the set {k(i),i<n}. |
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+0
2
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| 1, 5, 7, 10, 16, 24, 33, 43, 48, 60, 74, 89, 96, 112, 130, 150, 171, 193, 204, 228, 253, 279, 306, 334, 364, 396, 429, 463, 476, 511, 547, 564, 602, 641, 660, 700, 742, 786, 831, 877, 900, 948, 997, 1026, 1076, 1127, 1179, 1233, 1288, 1344, 1401, 1459, 1490
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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a(2) = 1+4 = 5 which is prime hence a(3) = 5+2 = 7 which is also a prime,a(4)= 7+3 = 10 which is composite hence a(5) = 10 + 6 = 16.
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MAPLE
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A073895 :=proc(nmax) local a, kset; a := [1] ; kset := {} ; while nops(a) < nmax do k :=2; while k in kset or isprime(k)<>isprime(op(-1, a)) do k := k+1 ; od ; a := [op(a), op(-1, a)+k] ; kset := kset union {k} ; od ; RETURN(a) ; end: op(A073895(80)) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 27 2007
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CROSSREFS
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Sequence in context: A020711 A133756 A048584 this_sequence A113194 A088768 A131998
Adjacent sequences: A073892 A073893 A073894 this_sequence A073896 A073897 A073898
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KEYWORD
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nonn,easy
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 18 2002
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 27 2007
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