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A061092
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a(0) = 1; for n>0, a(n) = smallest prime of the form k*a(n-1) + 1.
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19
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1, 2, 3, 7, 29, 59, 709, 2837, 22697, 590123, 1180247, 9441977, 169955587, 2719289393, 5438578787, 32631472723, 391577672677, 1566310690709, 50121942102689, 1503658263080671, 9021949578484027, 360877983139361081
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OFFSET
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0,2
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COMMENTS
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Dirichlet proved that for every prime p there exists at least one prime of the form kp + 1, hence the sequence is infinite.
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LINKS
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T. D. Noe, Table of n, a(n) for n = 0..100
Lejeune-Dirichlet, There are infinitely many prime numbers in all arithmetic progressions with first term and difference coprime, arXiv:0808.1408 (original 1837, translated from German)
Amarnath Murthy, On the divisors of Smarandache Unary Sequence. Smarandache Notions Journal, Vol. 11, No. 1-2-3, Spring 2000, page 184
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EXAMPLE
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59 = 2*29 + 1; 709 = 12*59 + 1.
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MATHEMATICA
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a[1] = 2; a[n_] := a[n] = Block[{k = 1, p = a[n - 1]}, While[ !PrimeQ[k*p + 1], k++ ]; k*p + 1]; Table[ a[n], {n, 21}] (* Robert G. Wilson v, Nov 26 2004 *)
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PROG
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(PARI) for (n=0, 100, if (n>0, k=1; while (!isprime(k*a + 1), k++); a=k*a + 1, a=1); write("b061092.txt", n, " ", a)) \\ Harry J. Smith, Jul 17 2009
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CROSSREFS
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Corresponding values of k are in A121799.
Sequence in context: A276665 A062573 A019435 * A084435 A072469 A004062
Adjacent sequences: A061089 A061090 A061091 * A061093 A061094 A061095
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy, Apr 19 2001
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EXTENSIONS
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More terms from Patrick De Geest, May 29 2001
Edited by Charles R Greathouse IV, Aug 02 2010
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STATUS
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approved
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