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 A087371 Smallest k such that 10^k + 2n-1 is a prime >10, or 0 if no such k exists. Index of the smallest power of 10 which when increased by the n-th odd number yields a prime. 1
 1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 2, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 2, 1, 0, 1, 0, 0, 1, 2, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 3, 2, 0, 0, 1, 0, 1, 2, 0, 1, 1, 0, 2, 0, 0, 1, 1, 0, 0, 1, 0, 2, 1, 0, 1, 4, 0, 1, 0, 0, 1, 1, 0, 0, 2, 0, 1, 1, 0, 1, 1, 0, 2, 0, 0, 6, 1, 0, 0, 2, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,20 COMMENTS Most of the terms are 0, 1 or 2. Subsidiary sequence: Index of the first occurrence of n. Conjecture: There exists a finite M such that a(n) < M for all n. LINKS EXAMPLE a(10) = 1 as 10^1 + 19 = 29 is a prime. CROSSREFS Sequence in context: A309475 A221314 A326642 * A307597 A307056 A112762 Adjacent sequences:  A087368 A087369 A087370 * A087372 A087373 A087374 KEYWORD nonn AUTHOR Amarnath Murthy, Sep 09 2003 EXTENSIONS More terms from David Wasserman, May 24 2005 STATUS approved

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Last modified October 23 20:17 EDT 2019. Contains 328373 sequences. (Running on oeis4.)