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Squares equal to the sum of the first k primes minus 1.
2

%I #13 Aug 10 2023 12:25:51

%S 1,4,9,16,196,839056,7796654478001

%N Squares equal to the sum of the first k primes minus 1.

%C No more terms < 7472966967498, sum of first 10^6 primes minus 1. - _Ray Chandler_, Oct 07 2005

%t Select[Accumulate[Prime[Range[1000]]]-1,IntegerQ[Sqrt[#]]&] (* _Harvey P. Dale_, Jun 09 2022 *)

%o (PARI) lista(nn) = my(s=-1); forprime(p=2, nn, s+=p; if(issquare(s), print1(s, ", "))) \\ _Jinyuan Wang_, Aug 10 2023

%Y Cf. A007504, A110997.

%Y Intersection of A000290 and A237589.

%K nonn,hard,more

%O 1,2

%A _Giovanni Teofilatto_, Sep 30 2005

%E a(6) corrected by _Ray Chandler_, Oct 07 2005

%E a(7) from _Jinyuan Wang_, Aug 10 2023