cp's OEIS Frontend

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.

A265402 Fixed points of A265388: numbers n for which gcd{k=1..n-1} binomial(2*n, 2*k) = n.

Original entry on oeis.org

11, 17, 23, 29, 43, 47, 53, 59, 67, 71, 73, 83, 89, 101, 103, 107, 109, 113, 127, 131, 137, 149, 151, 163, 167, 173, 179, 191, 193, 197, 223, 227, 233, 239, 241, 251, 257, 263, 269, 277, 281, 283, 293, 311, 317, 347, 349, 353, 359, 373, 383, 389, 397, 401, 409, 419, 431, 433, 443, 449, 457, 461, 463, 467, 479, 487, 491, 503
Offset: 1

Views

Author

Antti Karttunen, Dec 08 2015

Keywords

Crossrefs

Fixed points of A265388. Cf. also A265403.

Programs

  • Mathematica
    Select[Range@ 504, GCD @@ Array[Function[k, Binomial[2 #, 2 k]], {# - 1}] == # &] (* Michael De Vlieger, Dec 11 2015 *)
  • PARI
    isok(n) = (n>1) && gcd(vector(n-1, k, binomial(2*n, 2*k))) == n; \\ Michel Marcus, Dec 08 2015, edited by Antti Karttunen, Dec 11 2015 (see A265388 for why).