21451

Appears in sequences

• Values of m, the main key or generating number for Pythagorean triangles in which S (the odd short leg) and U (the hypotenuse) are twin primes.at n=43A051891
• Structured tetrakis hexahedral numbers (vertex structure 5).at n=18A100174
• Number of isomorphism classes of nanocones with 5 pentagons and a symmetric boundary of length n.at n=14A198086
• a(n) = floor(5*prime(n)^2 / 4).at n=31A246010
• Number of Motzkin excursions of length n with an even number of humps.at n=13A307564
• Centered 10-gonal numbers which are products of two primes.at n=28A367792