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).

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, 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, 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

Offset: 0

Author

Antti Karttunen, Nov 07 2015

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000005, A060990, A263087, A263251.

Cf. also A263252 (partial sums).

Programs

PARI

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.
A263087(n) = A060990(n^2);
A263250(n) = A263087(2*n);
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.

Scheme

(define (A263250 n) (A263087 (+ n n)))

Formula

a(n) = A263087(2*n).