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Search: id:A049232
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| A049232 |
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Primes p such that p+2 is divisible by a square. |
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+0
4
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| 2, 7, 23, 43, 47, 61, 73, 79, 97, 151, 167, 173, 223, 241, 277, 313, 331, 349, 359, 367, 373, 421, 439, 457, 523, 547, 601, 619, 673, 691, 709, 727, 733, 773, 823, 839, 853, 907, 929, 997, 1033, 1051, 1069, 1087, 1123, 1181, 1213, 1223, 1231, 1249, 1303
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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Abs[ mu[ Prime[ k ]+2 ]=0
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EXAMPLE
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47 is here because 47+2=49 is square; 523 is here since 523+2=525=25*21 is divided by a square
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MATHEMATICA
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(*in Mathematica6*)Select[Prime[Range[100]], ! SquareFreeQ[ # + 2] &] [From Zak Seidov (zakseidov(AT)yahoo.com), Oct 28 2008]
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PROGRAM
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(PARI) powerfreep3(n, p, k) = { c=0; pc=0; forprime(x=2, n, pc++; if(ispowerfree(x+k, p)==0, c++; print1(x", "); ) ); print(); print(c", "pc", "c/pc+.0) } ispowerfree(m, p1) = { flag=1; y=component(factor(m), 2); for(i=1, length(y), if(y[i] >= p1, flag=0; break); ); return(flag) }
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CROSSREFS
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A091880 gives prime indices.
Sequence in context: A106020 A045383 A089176 this_sequence A100917 A049552 A049572
Adjacent sequences: A049229 A049230 A049231 this_sequence A049233 A049234 A049235
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu)
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EXTENSIONS
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Corrected by Cino Hilliard (hillcino368(AT)gmail.com) and Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 08 2003
Edited by N. J. A. Sloane (njas(AT)research.att.com), Oct 27 2008 at the suggestion of R. J. Mathar.
Mathematica program from [From Zak Seidov (zakseidov(AT)yahoo.com), Oct 28 2008]
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