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A256917
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Primes which are not the sums of two consecutive nonsquares.
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1
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2, 3, 7, 17, 19, 31, 71, 73, 97, 127, 163, 199, 241, 337, 449, 577, 647, 881, 883, 967, 1151, 1153, 1249, 1459, 1567, 1801, 2179, 2311, 2591, 2593, 2887, 3041, 3361, 3527, 3529, 3697, 4049, 4051, 4231, 4801, 4999, 5407, 6271, 6961, 7687, 7937, 8191, 8713, 9521, 10369, 10657
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OFFSET
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1,1
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COMMENTS
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The sums of two consecutive nonsquares are 5, 8, 11, 13, 15, 18, 21, 23, 25, 27, 29, 32, 35, 37, ...
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LINKS
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EXAMPLE
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2, 3, 7 are in this sequence because first three sums of two consecutive nonsquares are 5, 8, 11 and 2, 3, 7 are primes.
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MATHEMATICA
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Union[{2}, Select[Table[2n^2-1, {n, 0, 1000}], PrimeQ], Select[Table[2n^2+1, {n, 0, 1000}], PrimeQ]] (* Ivan N. Ianakiev, Apr 24 2015 *)
Module[{nn=11000, ns}, ns=Total/@Partition[Select[Range[nn], !IntegerQ[Sqrt[#]]&], 2, 1]; Complement[ Prime[Range[PrimePi[Last[ns]]]], ns]] (* Harvey P. Dale, Mar 06 2024 *)
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PROG
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(PARI)
a256917(maxp) = {
ps=[2];
k=1; while((t=2*k^2-1)<=maxp, k++; if(isprime(t), ps=setunion(ps, [t])));
k=1; while((t=2*k^2+1)<=maxp, k++; if(isprime(t), ps=setunion(ps, [t])));
ps
}
(PARI) list(lim)=my(v=List([2]), t); for(k=2, sqrtint((lim+1)\2), if(isprime(t=2*k^2-1), listput(v, t))); for(k=1, sqrtint((lim-1)\2), if(isprime(t=2*k^2+1), listput(v, t))); Set(v) \\ Charles R Greathouse IV, Apr 23 2015
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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