

A085902


a(0) = 2, a(n) is the smallest squarefree number > a(n1) such that the sum a(n) + a(i) for all i = 1 to (n1) is squarefree. Or, sum of any two terms is a squarefree number.


4



2, 3, 11, 19, 55, 59, 83, 111, 127, 155, 163, 199, 203, 219, 263, 299, 307, 311, 371, 383, 399, 455, 515, 803, 883, 919, 983, 1063, 1499, 1559, 1927, 2019, 2063, 2183, 2215, 2271, 2359, 2503, 2703, 2755, 2999, 3459, 3899, 3927, 4271, 4303, 4411, 4519, 4559
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OFFSET

0,1


COMMENTS

It can easily be proved that a(n) == 3 (mod 4) for all n > 2.


LINKS



MATHEMATICA

a[0] = 2; a[n_] := a[n] = Module[{t = Array[a, n, 0], k = a[n  1] + 1}, While[! SquareFreeQ[k]  AnyTrue[t, ! SquareFreeQ[k + #] &], k++]; k]; Array[a, 100, 0] (* Amiram Eldar, Aug 21 2023 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



