180300

Appears in sequences

• Triangular numbers whose digit reversal is also a triangular number.at n=25A061455
• Nonpalindromic triangular numbers whose digit reversal is also a triangular number (possibly with fewer digits).at n=11A069673
• a(n) = p(n)*(p(n)-1)/2 where p(n) = upper member of n-th pair of twin primes.at n=26A082669
• a(n) = (n+1)^2*(n+2)*(5*n^2 + 15*n + 12)/24.at n=14A108676
• a(n) = n*(n+1)*(n^2+n+1)/2.at n=24A110450
• Triangular numbers for which the number of divisors is also a triangular number.at n=36A116541
• Triangular numbers for which the sum of the digits is a pentagonal number.at n=35A117305
• Smallest triangular number whose decimal expansion ends (nontrivially) with the n-th triangular number.at n=23A229262
• Let x(0)x(1)x(2)... x(q) denote the decimal expansion of n. Sequence lists the numbers n such that the suffix of decimal expansion x(2)... x(q) is the p-th divisor of n where p is the prefix of decimal expansion x(0)x(1).at n=20A234315
• Numbers k such that the symmetric representation of sigma(k) has only two parts and they meet at the center of the Dyck path.at n=29A262259