39557

Appears in sequences

• Triangle read by rows: T(n,k), n >=1, 0 <= k <= C(n,k), = number of n X n symmetric positive semi-definite matrices with 2's on the main diagonal and 1's and 0's elsewhere and with k 1's above the diagonal.at n=47A083029
• a(n) is number of solutions of the equation sigma(x)=10^n.at n=30A110078
• Numbers n such that n^2 + 1 is divisible by a 5th power.at n=25A218564
• Number of steps needed when starting from (3^(n+1))-1 and repeatedly applying the map that replaces k with k - (sum of digits in base-3 representation of k) to encounter the first number whose base-3 representation begins with a digit other than 2.at n=12A261237
• a(n) = Sum_{k=1..n} sigma(n*k).at n=32A372710