A276962 - OEIS

A276962

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

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

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OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..45.

EXAMPLE

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.

MATHEMATICA

Select[Range[3000], PrimeOmega[#^17-1] == 2 &]

PROG

(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

CROSSREFS

Cf. A001358, A010805, A104494.

Sequence in context: A041780 A041782 A041784 * A105092 A112144 A007248

Adjacent sequences: A276959 A276960 A276961 * A276963 A276964 A276965

KEYWORD

nonn

AUTHOR

Gary E. Davis, Sep 22 2016

EXTENSIONS

More terms from Altug Alkan, Sep 30 2016

STATUS

approved