239800

Appears in sequences

• A014486-encoding of symmetric binary trees.at n=18A083941
• Pentagonal numbers for which both the sum of the digits and the product of the digits are pentagonal numbers.at n=23A117711
• Indices among the primes of the primes in A020461.at n=15A138126
• Number of 2 X 2 matrices having all terms in {1,...,n} and determinant >= 2n.at n=27A211062
• a(n) = n^2*(3*n^2 - 1)/2.at n=20A260810
• Expansion of e.g.f. log( 1 + (exp(x) - 1)^5 / 5! ).at n=6A346977