This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A048196 #33 May 20 2018 03:24:04 %S A048196 14,22,33,42,44,56,57,59,74,107,113,115,1568,1571 %N A048196 Numbers k for which binomial(k, floor(k/2)) has the same number of unitary and non-unitary divisors. %C A048196 Next term > 10^8. - _David A. Corneth_, May 14 2018 %C A048196 Numbers k where b = binomial(k, floor(k/2)) is of the form p_i ^ e_i where p_i is the i-th prime in the factorization of b, e_i = 1 except exactly one e_i = 3 for i > 1. - _David A. Corneth_, May 13 2018 %H A048196 David A. Corneth, <a href="/A048196/a048196_1.gp.txt">PARI link</a> %F A048196 A034444(A001405(k)) = A048105(A001405(k)). %e A048196 At k=59, the corresponding binomial coefficient, binomial(59,29) has 8192 divisors, of which 4096 are unitary and 4096 are not. %o A048196 (PARI) isok(n) ={ n=binomial(n, floor(n/2)); sumdiv(n, d, issquarefree(d)) == sumdiv(n, d, !issquarefree(d)); } \\ _Joerg Arndt_, May 13 2018 %o A048196 (PARI) \\ much faster: %o A048196 isok(n) ={ n=binomial(n, floor(n/2)); my(u=1<<omega(n)); u==numdiv(n)-u; } \\ _Joerg Arndt_, May 13 2018 %o A048196 (PARI) \\ for a still faster program see the Corneth link. %Y A048196 Cf. A001405, A034444, A034973, A048105, A048109. %K A048196 nonn,hard %O A048196 1,1 %A A048196 _Labos Elemer_ %E A048196 a(9) .. a(14) from _Joerg Arndt_, May 13 2018