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a(n) is the third term in Euclid-Mullin (EM) prime sequence initiated with n-th prime.
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6
7, 7, 11, 3, 23, 3, 5, 3, 47, 59, 3, 3, 83, 3, 5, 107, 7, 3, 3, 11, 3, 3, 167, 179, 3, 7, 3, 5, 3, 227, 3, 263, 5, 3, 13, 3, 3, 3, 5, 347, 359, 3, 383, 3, 5, 3, 3, 3, 5, 3, 467, 479, 3, 503, 5, 17, 7, 3, 3, 563, 3, 587, 3, 7, 3, 5, 3, 3, 5, 3, 7, 719, 3, 3, 3, 13, 19, 3, 11, 3, 839, 3, 863
EXAMPLE
First term is p[n], 2nd equals 2; 3rd term is given here as largest p-divisor of 2p+1 [occasionally safe primes, A005385];
MATHEMATICA
a[x_]:=First[Flatten [FactorInteger[Apply[Times, Table[a[j], {j, 1, x-1}]]+1]]]; ta=Table[0, {168}]; a[1]=1; Do[{a[1]=Prime[j], el=10}; Print[a[el]; ta[[j]]=a[el]; j++ ], {j, 1, 168}]; ta
a[n] is the 5th term in Euclid-Mullin (EM) prime sequence initiated with n-th prime.
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4
13, 13, 331, 13, 7, 6163, 7, 571, 13, 10267, 23, 31, 7, 13, 17, 7, 3, 7, 5227, 43, 7, 2371, 7, 61, 19, 3, 7, 13, 3271, 13, 5, 37, 4111, 43, 3, 13, 47, 7, 5011, 360187, 7, 73, 13, 22003, 23, 7, 8863, 5, 7, 6871, 181, 193, 7, 7, 11, 139, 3, 7, 1297, 73, 7, 7, 31, 3, 7
EXAMPLE
First term is p[n], 2nd equals 2;
3rd term is A091460 as largest p-divisor of 2p+1 (occasionally safe primes, A005385);
MATHEMATICA
a[x_]:=First[Flatten [FactorInteger[Apply[Times, Table[a[j], {j, 1, x-1}]]+1]]]; ta=Table[0, {168}]; a[1]=1; Do[{a[1]=Prime[j], el=5}; Print[a[el]; ta[[j]]=a[el]; j++ ], {j, 1, 168}]; ta
a(n) is the 7th term in Euclid-Mullin (EM) prime sequence initiated with n-th prime.
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4
5, 5, 199, 5, 433, 1601, 31, 457, 7109609443, 5, 7, 127, 71, 5, 7, 2620003, 4583, 1217, 5, 67, 6729871, 39334891, 5, 53, 461, 449885311, 1511, 197, 7, 22008559, 19, 1249, 7, 7, 3217, 7, 7, 3931, 7, 110663370509047, 375155719, 29, 28529671, 23, 24603331
EXAMPLE
First term is p(n), 2nd equals 2;
3rd term is A091460 as largest p-divisor of 2p+1 (occasionally safe primes, A005385);
MATHEMATICA
a[x_]:=First[Flatten [FactorInteger[Apply[Times, Table[a[j], {j, 1, x-1}]]+1]]]; ta=Table[0, {168}]; a[1]=1; Do[{a[1]=Prime[j], el=6}; Print[a[el]; ta[[j]]=a[el]; j++ ], {j, 1, 168}]; ta
a(n) is the 6th term in Euclid-Mullin (EM) prime sequence initiated with n-th prime.
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3
53, 53, 19, 53, 10627, 7, 3571, 271, 84319, 7, 47059, 7, 47, 53, 23971, 11, 13, 5, 7, 201499, 5, 7, 67, 13, 7, 21211, 5, 29, 10696171, 11, 149, 971, 16896211, 11, 58111, 17, 11, 75307, 25105111, 853, 139, 7, 5, 613, 181, 23, 13, 29, 13, 19, 53, 47, 5, 11, 84811
EXAMPLE
First term is p(n), 2nd equals 2;
3rd term is A091460 as largest p-divisor of 2p+1 (occasionally safe primes, A005385);
MATHEMATICA
a[x_]:=First[Flatten [FactorInteger[Apply[Times, Table[a[j], {j, 1, x-1}]]+1]]]; ta=Table[0, {168}]; a[1]=1; Do[{a[1]=Prime[j], el=6}; Print[a[el]; ta[[j]]=a[el]; j++ ], {j, 1, 168}]; ta
a(n) is the position of the prime 5 in the Euclid-Mullin (EM) sequence of type A000945, if it were started with prime(n) instead of 2.
+10
2
7, 7, 1, 7, 18, 10, 3, 4, 11, 7, 8, 8, 10, 7, 3, 13, 8, 6, 7, 8, 6, 4, 7, 8, 9, 4, 6, 3, 4, 11, 5, 8, 3, 4, 4, 8, 8, 13, 3, 10, 21, 15, 6, 8, 3, 4, 13, 5, 3, 4, 8, 14, 6, 10, 3, 6, 12, 6, 10, 6, 6, 13, 8, 4, 6, 3, 11, 5, 3, 4, 13, 6, 10, 8, 4, 26, 8, 7, 11, 4, 7, 10, 7, 5, 4, 7, 16, 8, 7, 9, 3, 5, 5, 6
COMMENTS
a(38) = 13 because prime(38) = 163 and the corresponding EM sequence is {163, 2, 3, 11, 7, 75307, 3931, 5399, 3041, 409, 179, 92958641873, 5, 2003, ...}, where 5 appears at the 13th position. - David Wasserman, Apr 19 2007
PROG
(PARI) em(i) = local(p, c, n, f, q); p = prime(i); if (p == 5, return(1)); c = 1; n = p; while (1, c++; f = factor(n + 1, 2^31 - 1); q = f[1, 1]; if (!isprime(q), f = factor(n + 1); q = f[1, 1]); if (q == 5, return(c)); n *= q); \\ David Wasserman, Apr 19 2007
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