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 A048197 #21 Jul 22 2024 15:22:27 %S A048197 1,2,3,4,5,6,7,8,9,11,12,13,15,16,17,18,19,20,21,23,24,31,32,35,39,41, %T A048197 43,55,65,67,71,72,73,79,131,271,1567 %N A048197 Numbers k for which binomial(k, floor(k/2)) has more unitary than non-unitary divisors. %C A048197 A048107 is applied to central binomial coefficients. This sequence includes the 12 known squarefree central binomial coefficients, i.e., 1, 2, 3, 4, 5, 7, 8, 11, 17, 19, 23, 71 collected in A046098. %C A048197 Numbers k such that A034444(A001405(k)) > A048105(A001405(k)). %C A048197 No more terms below 10^5. - _Ivan Neretin_, Sep 06 2015 %e A048197 For k = 59 the corresponding binomial(59,29) has 8192 divisors, of which 4096 are unitary and equally 4096 are non-unitary. So 59 is not in the sequence. %t A048197 Select[Range[60], Function[n, r = Binomial[n, Floor[n/2]]; 2^(PrimeNu[r] + 1) > DivisorSigma[0, r]]] (* _Ivan Neretin_, Sep 06 2015 *) %o A048197 (PARI) is(n) = apply(x -> 2^(omega(x)+1) - numdiv(x), binomial(n, n\2)) > 0; \\ _Amiram Eldar_, Jul 22 2024 %Y A048197 Cf. A001405, A034444, A048107, A046098. %K A048197 nonn,more %O A048197 1,2 %A A048197 _Labos Elemer_ %E A048197 More terms from _Ivan Neretin_, Sep 06 2015