1718721

Appears in sequences

• Numbers k such that the sets of prime factors (ignoring multiplicity) of A000203(k) = sigma(k) and of A001157(k) = sigma_2(k) are identical.at n=16A081380
• Squares k such that k - 2 and k + 2 are prime.at n=26A144938
• Squares not divisible by 10 with digits d_1, d_2, ... d_k such that d_1^2 + ... + d_k^2 is a square.at n=42A254959