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A256163 Odd numbers n such that for all 2^k < n the numbers n + 2^k, n - 2^k, n*2^k + 1, and n*2^k - 1 are composite. 4
1, 7913, 8923, 24943, 34009, 35437, 42533, 52783, 60113, 83437, 100727, 105953, 116437, 120521, 126631, 132211, 133241, 137171, 145589, 164729, 172331, 181645, 183671, 192173, 196633, 199513, 203069, 204013, 215113, 215279, 218503, 220523, 253519, 254329, 254587 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Felix Fröhlich, Table of n, a(n) for n = 1..10000

PROG

(MAGMA) lst:=[]; for n in [1..254587 by 2] do t:=0; k:=0; while 2^k lt n do if IsPrime(n-2^k) or IsPrime(n+2^k) or IsPrime(n*2^k-1) or IsPrime(n*2^k+1) then t:=1; break; end if; k+:=1; end while; if IsZero(t) then Append(~lst, n); end if; end for; lst;

(PARI) for(n=1, 1e6, if(n%2==1, k=0; prim=0; while(2^k < n, if(ispseudoprime(n+2^k) || ispseudoprime(n-2^k) || ispseudoprime(n*2^k+1) || ispseudoprime(n*2^k-1), prim++; break({1})); k++); if(prim==0, print1(n, ", ")))) \\ Felix Fröhlich, Apr 01 2015

CROSSREFS

Cf. A006285, A076335.

Subsequence of A255967.

A256237 gives the primes.

Sequence in context: A115426 A206069 A237969 * A171111 A155178 A031922

Adjacent sequences:  A256160 A256161 A256162 * A256164 A256165 A256166

KEYWORD

nonn

AUTHOR

Arkadiusz Wesolowski, Mar 17 2015

STATUS

approved

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Last modified October 21 21:46 EDT 2019. Contains 328315 sequences. (Running on oeis4.)