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%I #13 Mar 12 2020 09:04:38
%S 0,1,4,8,9,10,16,18,20,26,32,34,36,40,45,49,52,58,64,68,72,74,80,81,
%T 82,90,98,104,106,116,117,121,122,128,136,144,146,148,153,160,162,164,
%U 178,180,194,196,202,208,212,218,226,232,234,242,244,245,256,261,272,274
%N Nonprime numbers with a unique partition as a sum of 2 squares x^2 + y^2.
%H Amiram Eldar, <a href="/A124982/b124982.txt">Table of n, a(n) for n = 1..10000</a>
%F A000161(a(n)) = 1. - _R. J. Mathar_, Nov 29 2006
%t Select[Range[0, 300], !PrimeQ[#] && Length @ PowersRepresentations[#, 2, 2] == 1 &] (* _Amiram Eldar_, Mar 12 2020 *)
%o (PARI) A000161(n)={ local(cnt=0,y2) ; for(x=0,floor(sqrt(n)), y2=n-x^2 ; if( y2>=x^2 && issquare(y2), cnt++ ; ) ; ) ; return(cnt) ; } isA124982(n)= { if( isprime(n), return(0), if(A000161(n)==1, return(1), return(0) ) ) ; } { for(n=0,300, if( isA124982(n), print1(n,", ") ; ) ; ) ; } \\ _R. J. Mathar_, Nov 29 2006
%Y Cf. A000161, A002145.
%K nonn
%O 1,3
%A _Artur Jasinski_, Nov 16 2006
%E Corrected and extended by _R. J. Mathar_, Nov 29 2006
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