253116

Appears in sequences

• Smallest triangular number beginning with the n-th triangular number other than itself.at n=21A072517
• Smallest triangular numbers whose decimal expansion begins (nontrivially) with n-th triangular number.at n=21A229235
• Refactorable triangular numbers.at n=31A272524
• Triangular numbers k such that psi(k) is a square, where psi(k) is the Dedekind psi function (A001615).at n=38A292064
• Integers that concatenate 3 counts: the number of terms in the sequence so far, the number of primes in the sequence so far, the number of digits in the sequence so far, with a(1)= 113. The sequence is always extended with the smallest available integer not leading to a contradiction or a dead end.at n=24A309617
• Triangular numbers such that the three numbers before it and the three numbers after it are squarefree.at n=18A374393