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 A089212 Primes p such that p-1 and p+1 are divisible by a fifth power. 6
 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; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE 13121 is a term since 13121 - 1 = 2^6 * 5 * 41, 13121 + 1 = 2 * 3^8. MATHEMATICA 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 (* Vladimir Joseph Stephan Orlovsky, Oct 03 2009 *) PROG (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) } CROSSREFS Cf. A075432, A086708, A086709. Sequence in context: A250904 A250948 A157433 * A023320 A206149 A221156 Adjacent sequences:  A089209 A089210 A089211 * A089213 A089214 A089215 KEYWORD easy,nonn AUTHOR Cino Hilliard, Dec 09 2003 STATUS approved

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Last modified June 3 05:29 EDT 2020. Contains 334798 sequences. (Running on oeis4.)