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.

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

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