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%I #7 Oct 19 2019 03:20:00
%S 2,6,11,24,42,121,30,319,99,1592,344,574,3786,4196,650,4619,217,1532,
%T 11244,5349,8081,3861,12751,18281,9221,5995,22467,16222,43969,35975,
%U 192603,108146,52313,218234,15927,132997,42673,78858,103865,84483
%N Least k such that gcd(prime(k+1)-1, prime(k)-1) = 2n.
%C Since all consecutive primes, p < q and p greater than 2, are odd, therefore gcd(p-1, q-1) must be even.
%e n=4: a(4) = 24 = gcd(89-1, 97-1) = gcd(p(24)-1, p(25)-1) = 8 = 2n.
%t a = Table[0, {100}]; p = 3; q = 5; Do[q = Prime[n + 1]; d = GCD[p - 1, q - 1]/2; If[d < 101 && a[[d]] == 0, a[[d]] = n]; b = c, {n, 2, 10^7}]; a
%Y Cf. A063444, A084307, A058263.
%K easy,nonn
%O 1,1
%A _Robert G. Wilson v_, Jan 31 2002
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