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Search: id:A105405
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| A105405 |
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Indices n of primes p(n), p(n+3) such that p(n)-1 and p(n+3)-1 have the same largest prime factor. |
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+0
1
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| 98, 156, 615, 1474, 2313, 66826, 82099, 150425, 188513, 274638, 321482, 523573, 874881, 6872507, 8101145, 22658038, 95011150, 159081273, 381064119, 509331868, 1216774420, 3067461737, 3356013378, 5447285266, 14949553319, 15007703651, 19495563000
(list; graph; listen)
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OFFSET
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2,1
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MATHEMATICA
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Do[p = Prime[n] - 1; q = Prime[n+3] - 1; l = Select[Divisors[p], PrimeQ]; m = Select[Divisors[q], PrimeQ]; If[Max[l] == Max[m], Print[n]], {n, 1, 10^7}] (Propper)
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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: A095589 A039491 A109553 this_sequence A044430 A044811 A063369
Adjacent sequences: A105402 A105403 A105404 this_sequence A105406 A105407 A105408
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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 Ryan Propper (rpropper(AT)stanford.edu), Sep 19 2005
a(17)-a(28) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 03 2008
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