247009

Appears in sequences

• Triangular numbers + 1 squared.at n=31A086601
• Number of (n+3) X 8 0..2 matrices with each 4 X 4 subblock idempotent.at n=18A224725
• Numbers k such that concat(k, d(k)) and concat(d(k), k) are both prime, where d(k) is the number of divisors of k.at n=16A284643
• Odd squares k for which A379113(k) > 1, i.e., k that have a proper unitary divisor d > 1 such that A048720(A065621(sigma(d)),sigma(k/d)) is equal to sigma(k).at n=8A379121