22578

Appears in sequences

• Numbers whose sum of divisors is a sixth power.at n=5A019424
• Numbers whose sum of divisors is 6^6 = 46656.at n=2A048256
• a(n) = 25*n*(n + 1)/2 + 3.at n=42A061793
• Least number starting a chain of exactly n consecutive even integers that do not have cototient-inverses.at n=5A072296
• Triangular numbers with palindromic indices.at n=30A089717
• Triangular numbers that are sandwiched between two semiprimes; or triangular numbers t such that t-1 and t+1 are both semiprime.at n=11A121898
• Triangular numbers n*(n+1)/2 with n and n+1 composite, where number of prime factors in n > number of prime factors in n+1.at n=40A144523
• Triangular numbers t such that all the digits needed to write the consecutive triangular numbers from 0 to t fill exactly an equilateral triangle (no holes, no overlaps).at n=16A158030
• Triangular numbers which are sums of 4 consecutive primes.at n=8A173420
• a(n) = smallest k having at least three prime divisors d such that (d + n) | (k + n).at n=31A202158
• Triangular numbers with digits in nondecreasing order.at n=24A234848
• Triangular numbers n such that sigma(n) is a square number.at n=7A256151
• Triangular numbers k such that psi(k) is a square, where psi(k) is the Dedekind psi function (A001615).at n=16A292064
• Numbers whose sum of divisors is the sixth power of one of their divisors.at n=3A303996
• Triangular numbers that are the product of four distinct primes.at n=29A333771
• Numbers whose sum of even digits and sum of odd digits are equal and whose digits are in nondecreasing order.at n=40A340125
• Integers m such that A342805(m) = m+3.at n=22A342806
• Triangular numbers (A000217) whose second arithmetic derivative (A068346) is also a triangular number.at n=38A351131
• Second hexagonal numbers having middle divisors.at n=35A361209
• Triangular numbers that are sandwiched between two squarefree semiprimes.at n=9A375384