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Search: id:A105408
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| A105408 |
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Indices n of primes p(n), p(n+4) such that p(n)+1 and p(n+4)+1 have the same largest prime factor. |
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1
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| 1, 3, 5, 16, 64, 85, 266, 547, 1709, 1771, 4415, 9545, 13129, 24130, 34201, 213122, 396981, 543586, 555301, 609182, 1040051, 1870869, 2547634, 3052012, 5076662, 8530768, 9773479, 18563382, 26505870, 89046072, 169660944, 193691856, 200228233, 359241899, 597825925, 914450195, 1020520062, 1585841242, 1970793485
(list; graph; listen)
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OFFSET
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2,2
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EXAMPLE
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p(1)+1=3 and p(5)+1=12 have the same largest prime factor.
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PROGRAM
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(PARI) \prime indices such that gd of prime(x)+ k and prime(x+m) + k are equal divpm1(n, m, k) = { local(x, l1, l2, v1, v2); for(x=2, n, v1 = ifactor(prime(x)+ k); v2 = ifactor(prime(x+m)+k); l1 = length(v1); l2 = length(v2); if(v1[l1] == v2[l2], print1(x", ") ) ) } ifactor(n) = \Vector of the prime factors of n { local(f, j, k, flist); flist=[]; f=Vec(factor(n)); for(j=1, length(f[1]), for(k = 1, f[2][j], flist = concat(flist, f[1][j]) ); ); return(flist) }
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CROSSREFS
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Sequence in context: A121646 A099101 A038120 this_sequence A085418 A139427 A035089
Adjacent sequences: A105405 A105406 A105407 this_sequence A105409 A105410 A105411
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KEYWORD
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nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), May 01 2005
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EXTENSIONS
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More terms from Erich Friedman (efriedma(AT)stetson.edu), Aug 26 2005
Corrected and extended by Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 03 2008
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