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Search: id:A089212
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| A089212 |
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Primes p such that p-1 and p+1 are divisible by a fifth power. |
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+0
5
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| 13121, 20897, 25759, 75329, 80191, 106433, 118751, 137537, 153089, 157951, 176417, 191969, 196831, 207521, 212383, 215297, 230849, 243487, 251263, 274591, 281249, 285281, 313471, 318751, 321247, 324161, 331937, 336799, 347489, 378593
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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13121 - 1 = 2^6*5*41, 13122 + 1 = 2*3^8
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MATHEMATICA
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f[n_]:=Max[Last/@FactorInteger[n]]; lst={}; Do[p=Prime[n]; If[f[p-1]>=5&&f[p+1]>=5, AppendTo[lst, p]], {n, 8!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Oct 03 2009]
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PROGRAM
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(PARI) \Input no. of iterations n, power p and number to subtract and add k. powerfreep4(n, p, k) = { c=0; pc=0; forprime(x=2, n, pc++; if(!ispowerfree(x-k, p) && !ispowerfree(x+k, p), 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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Sequence in context: A111887 A015341 A157433 this_sequence A023320 A068760 A102331
Adjacent sequences: A089209 A089210 A089211 this_sequence A089213 A089214 A089215
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Dec 09 2003
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