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%I #31 Sep 08 2022 08:45:11
%S 1,2,3,2,6,10,9,5,4,15,26,28,21,11,8,9,30,51,17,36,61,20,14,78,73,51,
%T 26,54,82,105,32,22,69,14,75,126,131,41,28,29,90,163,96,145,99,83,88,
%U 56,114,172,39,120,217,42,43,44,135,226,208,141,85,21,77,156,235,68,276
%N Multiplicative inverse of the n-th prime prime(n) modulo prime(n-1).
%H Charles R Greathouse IV, <a href="/A087454/b087454.txt">Table of n, a(n) for n = 2..10000</a>
%e We have a(7) = 10 because prime(7)*10 = 170 = 1 [mod 13] = 1 [mod prime(6)].
%p seq(`mod`(1/ithprime(n), ithprime(n-1)), n = 2..70); # _G. C. Greubel_, Aug 09 2019
%t Table[PowerMod[Prime[n], -1, Prime[n - 1]], {n, 2, 68}] (* _Geoffrey Critzer_, May 16 2015 *)
%o (PARI) a(n)=my(p=prime(n-1),g=nextprime(p+1)-p);lift(Mod(1/g,p)) \\ _Charles R Greathouse IV_, Aug 23 2011
%o (Magma) [InverseMod(NthPrime(n), NthPrime(n-1)): n in [2..70]]; // _G. C. Greubel_, Aug 09 2019
%o (Sage) [nth_prime(n).inverse_mod(nth_prime(n-1)) for n in (2..70)] # _G. C. Greubel_, Aug 09 2019
%Y Cf. A069830, A077005.
%K nonn,look
%O 2,2
%A _Lekraj Beedassy_, Oct 23 2003
%E Corrected and extended by _Ray Chandler_, Oct 24 2003
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