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%I #15 Jun 29 2019 02:25:16
%S 341,13747,19951,35333,60787,137149,150851,387731,458989,617093,
%T 769757,1104349,1251949,1277179,1397419,1463749,1507963,1826203,
%U 2134277,2205967,2617451,2976487,3345773,4361389,6474691,6955541,8095447
%N Sarrus numbers k such that k-1 and k+1 have the same number of prime divisors (counted with multiplicity).
%H Amiram Eldar, <a href="/A086806/b086806.txt">Table of n, a(n) for n = 1..10000</a>
%e 341 is a pseudoprime to base 2 while 340 = 2^2*5*17 and 342 = 2*3^2*19 each have four primes dividing them.
%t PrimeFactorExponentsAdded[n_] := Plus @@ Flatten[ Table[ # [[2]], {1}] & /@ FactorInteger[n]]; Select[ Range[9224390], !PrimeQ[ # ] && PowerMod[2, # - 1, # ] == 1 && PrimeFactorExponentsAdded[ # - 1] == PrimeFactorExponentsAdded[ # + 1] & ]
%Y Intersection of A001567 and A280382.
%Y Cf. A001222.
%K nonn
%O 1,1
%A _Jason Earls_, Aug 05 2003
%E More terms from _Robert G. Wilson v_, Aug 13 2003