81003

Appears in sequences

• Triangular numbers whose sum of aliquot divisors is a prime number.at n=32A083676
• Numbers that cannot be expressed as a sum of 2 triangular numbers and a power of 2.at n=17A112665
• Expansion of 2/((2+x)*sqrt(1-4*x)-x).at n=9A116396
• Triangular numbers for which the sum of the digits is a pentagonal number.at n=31A117305
• Triangular numbers T such that T+10 is the next prime after T.at n=15A129540
• a(n) = sqrt(sigma(2*m^2)), where m = A097023(n), i.e., sigma(2*m^2) is a square.at n=9A163764
• Integers m such that A342805(m) = m+3.at n=36A342806
• Numbers that start a run of four consecutive triangular numbers with four distinct prime factors.at n=13A349773