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 A074973 Smallest index i such that next_prime( 2*prime(i) ) - 2*prime(i) = 2n - 1. 0
 1, 4, 11, 20, 17, 67, 104, 56, 125, 165, 182, 316, 236, 359, 407, 1254, 667, 836, 1521, 1210, 1966, 3197, 1520, 2294, 2279, 2046, 5410, 5472, 1965, 6702, 13947, 10138, 12122, 16760, 7659, 22325, 16784, 13072, 36169, 17852, 15414, 69872, 23814, 16370, 46752 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS First index i such that NextPrime[p2=2*Prime[i]]-p2 is 2n-1; case n=1 corresponds to Sophie Germain (SG) primes, others may be called SG n-primes. Distance between 2*(n-th prime) and next prime in A059787. LINKS EXAMPLE a(54) = 342337 because difference between 2*p(342337) and next prime is 2*54 -1 = 107 and 342337 is the smallest such index. PROG (PARI) a(n) = {i = 1; while (nextprime(p2=2*prime(i)) - p2 != 2*n-1, i++); i; } \\ Michel Marcus, Oct 03 2013 (MAGMA) S:=[]; i:=1; for n in [1..45] do    while not NextPrime(2*NthPrime(i))-2*NthPrime(i) eq 2*n-1 do         i:=i+1;    end while;    Append(~S, i);    i:=1; end for; S;  // Bruno Berselli, Oct 03 2013 CROSSREFS Cf. A059787. Sequence in context: A009908 A321643 A049935 * A327457 A025526 A301093 Adjacent sequences:  A074970 A074971 A074972 * A074974 A074975 A074976 KEYWORD nonn AUTHOR Zak Seidov, Oct 06 2002 EXTENSIONS a(44)-a(45) from Bruno Berselli, Oct 03 2013 STATUS approved

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Last modified December 7 20:21 EST 2019. Contains 329847 sequences. (Running on oeis4.)