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Search: id:A103506
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| A103506 |
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a(n) = Smallest prime p, such that 2n+1 = 2*A000040(k) + p for some k>1, 0 if no such prime exists. |
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4
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| 0, 0, 0, 3, 5, 3, 5, 3, 5, 7, 13, 3, 5, 3, 5, 7, 13, 3, 5, 3, 5, 7, 13, 3, 5, 7, 17, 11, 13, 3, 5, 3, 5, 7, 13, 11, 13, 3, 5, 7, 37, 3, 5, 3, 5, 7, 13, 3, 5, 7, 17, 11, 13, 3, 5, 7, 29, 11, 13, 3, 5, 3, 5, 7, 13, 11, 13, 3, 5, 7, 37, 3, 5, 3, 5, 7, 13, 11, 13, 3, 5, 7, 61, 3, 5, 7, 17, 11, 13
(list; graph; listen)
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OFFSET
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1,4
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EXAMPLE
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For n < 4 there are no such primes, thus a(1)-a(3)=0. For n=4, 2*4+1 = 9 = 2*3+3, thus a(4)=3. For n=11, 2*11+1 = 23 = 2*5+13, thus a(11)=13.
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MATHEMATICA
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Do[m = 3; While[ ! (PrimeQ[m] && (((n - m)/2) > 2) && PrimeQ[(n - m)/2]), m = m + 2]; Print[m], {n, 9, 299, 2}]
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PROGRAM
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(Scheme:) (define (A103506 n) (let ((ind (A103509 n))) (if (zero? ind) 0 (A000040 ind))))
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CROSSREFS
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a(n)=0 if A103509(n)=0, otherwise A000040(A103509(n)). Cf. A103151, A103152, A103153.
Sequence in context: A010703 A107489 A152050 this_sequence A094929 A096634 A105439
Adjacent sequences: A103503 A103504 A103505 this_sequence A103507 A103508 A103509
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KEYWORD
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nonn
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AUTHOR
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Lei Zhou (lzhou5(AT)emory.edu), Feb 09 2005
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EXTENSIONS
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Edited and Scheme-code added by Antti Karttunen (His-Firstname.His-Surname(AT)gmail.com), Jun 19 2007
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