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A263250 Even bisection of A263087; number of solutions to x - d(x) = 4(n^2), where d(x) is the number of divisors of x (A000005).

%I A263250 #9 Nov 09 2015 16:06:30
%S A263250 2,1,1,0,0,0,2,0,0,0,0,0,2,0,0,1,1,0,2,1,1,1,1,0,2,0,1,0,0,0,0,0,1,1,
%T A263250 1,1,3,1,1,0,1,0,1,1,1,0,1,0,2,0,0,1,0,0,1,0,1,0,0,0,2,0,0,0,0,0,3,1,
%U A263250 1,1,0,0,1,1,0,0,1,1,1,0,1,1,0,1,2,0,0,0,1,0,2,0,0,1,0,0,1,1,2,1,1,0,2,1,1,0,0,1,1,0,0,1,1,0,0,0,1,0,1,0,1
%N A263250 Even bisection of A263087; number of solutions to x - d(x) = 4(n^2), where d(x) is the number of divisors of x (A000005).
%H A263250 Antti Karttunen, <a href="/A263250/b263250.txt">Table of n, a(n) for n = 0..10000</a>
%F A263250 a(n) = A263087(2*n).
%o A263250 (PARI)
%o A263250 A060990(n) = { my(k = n + 2400, s=0); while(k > n, if(((k-numdiv(k)) == n),s++); k--;); s}; \\ Hard limit A002183(77)=2400 good for at least up to A002182(77) = 10475665200.
%o A263250 A263087(n) = A060990(n^2);
%o A263250 A263250(n) = A263087(2*n);
%o A263250 p = 0; for(n=0, 10000, k = A263250(n); p += k; write("b263250.txt", n, " ", k); write("b263252.txt", n, " ", p)); \\ Compute A263250 and A263252 at the same time.
%o A263250 (Scheme) (define (A263250 n) (A263087 (+ n n)))
%Y A263250 Cf. A000005, A060990, A263087, A263251.
%Y A263250 Cf. also A263252 (partial sums).
%K A263250 nonn
%O A263250 0,1
%A A263250 _Antti Karttunen_, Nov 07 2015