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A103153
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a(n) = Smallest odd prime p, such that 2*n+1 = 2*p + A000040(k) for some k>1, 0 if no such prime exists.
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8
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0, 0, 0, 3, 3, 3, 5, 3, 3, 5, 3, 3, 5, 3, 7, 5, 3, 3, 5, 5, 3, 7, 3, 3, 5, 3, 7, 5, 3, 7, 5, 3, 3, 5, 5, 3, 7, 3, 3, 5, 5, 3, 7, 3, 19, 5, 3, 7, 5, 11, 3, 11, 3, 3, 5, 3, 3, 5, 3, 7, 5, 11, 7, 11, 11, 3, 11, 3, 13, 5, 3, 3, 5, 5, 7, 7, 3, 3, 5, 5, 3, 7, 5, 3, 7, 3, 13, 5, 3, 7, 5, 3, 3, 5, 5, 7, 7, 3
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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EXAMPLE
| 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=7, 2*7+1 = 15 = 2*5+5, thus a(7)=7.
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MATHEMATICA
| Do[m = 3; While[ ! (PrimeQ[m] && ((n - 2*m) > 2) && PrimeQ[n - 2*m]), m = m + 2]; Print[m], {n, 9, 299, 2}]
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PROG
| (Scheme:) (define (A103153 n) (let ((ind (A103507 n))) (if (zero? ind) 0 (A000040 ind))))
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CROSSREFS
| a(n)=0 if A103507(n)=0, otherwise A000040(A103507(n)). Cf. A103151, A103152, A002373.
Cf. A195352 (definition similar to this sequence, but p=2 allowed).
Sequence in context: A084742 A049613 A002373 * A162022 A096918 A075018
Adjacent sequences: A103150 A103151 A103152 * A103154 A103155 A103156
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KEYWORD
| nonn
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AUTHOR
| Lei Zhou (lzhou5(AT)emory.edu), Feb 09 2005
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EXTENSIONS
| Edited and Scheme-code added by Antti Karttunen (His-Firstname.His-Surname(AT)gmail.com), Jun 19 2007
Definition corrected by Hugo Pfoertner (hugo(AT)pfoertner.org), Sep 16 2011
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