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.

A276962 Numbers n such that n^17 - 1 is semiprime.

Original entry on oeis.org

20, 62, 84, 368, 410, 614, 720, 740, 762, 1230, 1280, 1988, 1998, 2064, 2100, 2268, 2312, 2468, 2678, 2940, 3002, 3324, 3392, 3462, 3768, 3848, 3968, 4178, 4244, 4680, 4968, 5022, 5024, 5198, 5304, 5382, 5624, 5822, 5850, 6048, 6248, 6338, 6354, 6398, 6428
Offset: 1

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Author

Gary E. Davis, Sep 22 2016

Keywords

Comments

Least number such that n^17-1 and n^17+1 are both semiprime is 93888. - Altug Alkan, Sep 30 2016

Examples

			a(1) = 20 because 20^17-1 = 13107199999999999999999 = 19*689852631578947368421 is the first occurrence of n^17 - 1 as a product of two distinct primes.
		

Crossrefs

Programs

  • Mathematica
    Select[Range[3000],PrimeOmega[#^17-1] == 2 &]
  • PARI
    isok(n) = bigomega(n^17-1)==2; \\ Michel Marcus, Sep 23 2016
    
  • PARI
    lista(nn) = forprime(p=2, nn, if(ispseudoprime(((p+1)^17-1)/p), print1(p+1, ", "))); \\ Altug Alkan, Sep 30 2016

Extensions

More terms from Altug Alkan, Sep 30 2016