cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A178375 The greatest common prime divisor of A000032(n)-1 and A001608(n), or 1 if no such divisor exists.

Original entry on oeis.org

2, 3, 2, 5, 1, 7, 2, 3, 1, 11, 1, 13, 1, 1, 2, 17, 1, 19, 1, 1, 2, 23, 1, 5, 1, 3, 1, 29, 1, 31, 2, 7, 1, 3, 1, 37, 1, 7, 1, 41, 1, 43, 2, 1, 2, 47, 1, 7, 2, 1, 3, 53, 1, 7, 1, 1, 2, 59, 1, 61, 1, 1, 2, 7, 1, 67, 3, 1, 1, 71, 1, 73, 2, 1, 1, 5, 1, 79, 1, 7, 1, 83, 1, 2, 2, 7, 2, 89, 1
Offset: 2

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Author

Vladimir Shevelev, May 26 2010

Keywords

Comments

If n is prime, then n divides c(n). If n is composite and divides c(n) it is a pseudoprime to both the Lucas (Bruckman) and Perrin tests, which is the intersection of A005845 and A013998.
Conjecture: Records of the sequence are consecutive primes.

Crossrefs

Cf. A000032, A001608, A178380, A005845, A013998.

Extensions

More terms from R. J. Mathar, Aug 08 2010
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