19755

Appears in sequences

• a(n) = Sum_{d|9} phi(d)*n^(9/d).at n=3A054608
• a(n) = Sum_{d|n} phi(d)*3^(n/d).at n=9A054610
• Triangle T(n,k) = Sum_{d|n} phi(d)*k^(n/d).at n=38A054618
• Take pairs (a, b), sorted on a, such that T(a)+T(b)=concatenation of a and b, where T(k) is the k-th triangular number A000217(k). Sequence gives values of a.at n=32A096031
• a(n) is the smallest positive integer which can be represented as the sum of distinct nonzero icosahedral numbers in exactly n ways, or -1 if no such integer exists.at n=12A360215