210276

Appears in sequences

• Triangular numbers such that both the number formed by the first floor((k+1)/2) digits and the remaining part (if any) are triangular numbers, where k is the number of digits.at n=18A068821
• a(1) = 1; a(n) is the smallest triangular number > a(n-1) which differs from it at every digit.at n=38A068855
• Smallest triangular number beginning with the n-th triangular number other than itself.at n=19A072517
• Triangular numbers which are 8-almost primes.at n=21A076582
• Smallest triangular numbers whose decimal expansion begins (nontrivially) with n-th triangular number.at n=19A229235
• Smallest triangular number whose decimal expansion ends (nontrivially) with the n-th triangular number.at n=22A229262
• Triangular numbers divisible by the square of the sum of their digits.at n=11A243008
• a(n) = n^2*(2*n^2 + (-1)^n).at n=18A275496